[PATCH v1] Improve the performance of --num-threads -d 31

[PATCH v1] Improve the performance of --num-threads -d 31

[Zhou Wenjian]

v1:
        1. change page_flag.ready's value to enum
        2. change the patch description
        3. cleanup some codes
	4. fix a bug in cyclic mode

multi-threads implementation will introduce extra cost when handling
each page. The origin implementation will also do the extra work for
filtered pages. So there is a big performance degradation in
--num-threads -d 31.
The new implementation won't do the extra work for filtered pages any
more. So the performance of -d 31 is close to that of serial processing.

The new implementation is just like the following:
        * The basic idea is producer producing page and consumer writing page.
        * Each producer have a page_flag_buf list which is used for storing
          page's description.
        * The size of page_flag_buf is little so it won't take too much memory.
        * And all producers will share a page_data_buf array which is
          used for storing page's compressed data.
        * The main thread is the consumer. It will find the next pfn and write
          it into file.
        * The next pfn is smallest pfn in all page_flag_buf.

Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>
---
 makedumpfile.c | 258 ++++++++++++++++++++++++++++++++++++++-------------------
 makedumpfile.h |  31 ++++---
 2 files changed, 193 insertions(+), 96 deletions(-)

diff --git a/makedumpfile.c b/makedumpfile.c
index fa0b779..0ecd065 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -3483,7 +3483,8 @@ initial_for_parallel()
 	unsigned long page_data_buf_size;
 	unsigned long limit_size;
 	int page_data_num;
-	int i;
+	struct page_flag *current;
+	int i, j;
 
 	len_buf_out = calculate_len_buf_out(info->page_size);
 
@@ -3562,8 +3563,10 @@ initial_for_parallel()
 		      - MAP_REGION * info->num_threads) * 0.6;
 
 	page_data_num = limit_size / page_data_buf_size;
+	info->num_buffers = 3 * info->num_threads;
 
-	info->num_buffers = MIN(NUM_BUFFERS, page_data_num);
+	info->num_buffers = MAX(info->num_buffers, NUM_BUFFERS);
+	info->num_buffers = MIN(info->num_buffers, page_data_num);
 
 	DEBUG_MSG("Number of struct page_data for produce/consume: %d\n",
 			info->num_buffers);
@@ -3588,6 +3591,36 @@ initial_for_parallel()
 	}
 
 	/*
+	 * initial page_flag for each thread
+	 */
+	if ((info->page_flag_buf = malloc(sizeof(void *) * info->num_threads))
+	    == NULL) {
+		MSG("Can't allocate memory for page_flag_buf. %s\n",
+				strerror(errno));
+		return FALSE;
+	}
+	memset(info->page_flag_buf, 0, sizeof(void *) * info->num_threads);
+
+	for (i = 0; i < info->num_threads; i++) {
+		if ((info->page_flag_buf[i] = malloc(sizeof(struct page_flag))) == NULL) {
+			MSG("Can't allocate memory for page_flag_buf. %s\n",
+				strerror(errno));
+			return FALSE;
+		}
+		current = info->page_flag_buf[i];
+
+		for (j = 1; j < NUM_BUFFERS; j++) {
+			if ((current->next = calloc(0, sizeof(struct page_flag))) == NULL) {
+				MSG("Can't allocate memory for data of page_data_buf. %s\n",
+					strerror(errno));
+				return FALSE;
+			}
+			current = current->next;
+		}
+		current->next = info->page_flag_buf[i];
+	}
+
+	/*
 	 * initial fd_memory for threads
 	 */
 	for (i = 0; i < info->num_threads; i++) {
@@ -3612,7 +3645,8 @@ initial_for_parallel()
 void
 free_for_parallel()
 {
-	int i;
+	int i, j;
+	struct page_flag *current;
 
 	if (info->threads != NULL) {
 		for (i = 0; i < info->num_threads; i++) {
@@ -3655,6 +3689,19 @@ free_for_parallel()
 		free(info->page_data_buf);
 	}
 
+	if (info->page_flag_buf != NULL) {
+		for (i = 0; i < info->num_threads; i++) {
+			for (j = 0; j < NUM_BUFFERS; j++) {
+				if (info->page_flag_buf[i] != NULL) {
+					current = info->page_flag_buf[i];
+					info->page_flag_buf[i] = current->next;
+					free(current);
+				}
+			}
+		}
+		free(info->page_flag_buf);
+	}
+
 	if (info->parallel_info == NULL)
 		return;
 
@@ -7076,10 +7123,10 @@ kdump_thread_function_cyclic(void *arg) {
 	void *retval = PTHREAD_FAIL;
 	struct thread_args *kdump_thread_args = (struct thread_args *)arg;
 	struct page_data *page_data_buf = kdump_thread_args->page_data_buf;
+	struct page_flag *page_flag_buf = kdump_thread_args->page_flag_buf;
 	struct cycle *cycle = kdump_thread_args->cycle;
-	int page_data_num = kdump_thread_args->page_data_num;
 	mdf_pfn_t pfn;
-	int index;
+	int index = kdump_thread_args->thread_num;
 	int buf_ready;
 	int dumpable;
 	int fd_memory = 0;
@@ -7125,47 +7172,47 @@ kdump_thread_function_cyclic(void *arg) {
 						kdump_thread_args->thread_num);
 	}
 
-	while (1) {
-		/* get next pfn */
-		pthread_mutex_lock(&info->current_pfn_mutex);
-		pfn = info->current_pfn;
-		info->current_pfn++;
-		pthread_mutex_unlock(&info->current_pfn_mutex);
+	/*
+	 * filtered page won't take anything
+	 * unfiltered zero page will only take a page_flag_buf
+	 * unfiltered non-zero page will take a page_flag_buf and a page_data_buf
+	 */
+	while (page_flag_buf->pfn < kdump_thread_args->end_pfn) {
+		buf_ready = FALSE;
 
-		if (pfn >= kdump_thread_args->end_pfn)
-			break;
+		while (page_data_buf[index].used != 0 ||
+				pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
+			index = (index + 1) % info->num_buffers;
 
-		index = -1;
-		buf_ready = FALSE;
+		page_data_buf[index].used = 1;
 
 		while (buf_ready == FALSE) {
 			pthread_testcancel();
-
-			index = pfn % page_data_num;
-
-			if (pfn - info->consumed_pfn > info->num_buffers)
+			if (page_flag_buf->ready == FLAG_READY)
 				continue;
 
-			if (page_data_buf[index].ready != 0)
-				continue;
-
-			pthread_mutex_lock(&page_data_buf[index].mutex);
+			/* get next pfn */
+			pthread_mutex_lock(&info->current_pfn_mutex);
+			pfn = info->current_pfn;
+			info->current_pfn++;
+			page_flag_buf->ready = FLAG_FILLING;
+			pthread_mutex_unlock(&info->current_pfn_mutex);
 
-			if (page_data_buf[index].ready != 0)
-				goto unlock;
+			page_flag_buf->pfn = pfn;
 
-			buf_ready = TRUE;
-
-			page_data_buf[index].pfn = pfn;
-			page_data_buf[index].ready = 1;
+			if (pfn >= kdump_thread_args->end_pfn) {
+				page_data_buf[index].used = 0;
+				page_flag_buf->ready = FLAG_READY;
+				info->current_pfn--;
+				break;
+			}
 
 			dumpable = is_dumpable(
 				info->fd_bitmap ? &bitmap_parallel : info->bitmap2,
 				pfn,
 				cycle);
-			page_data_buf[index].dumpable = dumpable;
 			if (!dumpable)
-				goto unlock;
+				continue;
 
 			if (!read_pfn_parallel(fd_memory, pfn, buf,
 					       &bitmap_memory_parallel,
@@ -7178,11 +7225,11 @@ kdump_thread_function_cyclic(void *arg) {
 
 			if ((info->dump_level & DL_EXCLUDE_ZERO)
 			    && is_zero_page(buf, info->page_size)) {
-				page_data_buf[index].zero = TRUE;
-				goto unlock;
+				page_flag_buf->zero = TRUE;
+				goto next;
 			}
 
-			page_data_buf[index].zero = FALSE;
+			page_flag_buf->zero = FALSE;
 
 			/*
 			 * Compress the page data.
@@ -7232,12 +7279,16 @@ kdump_thread_function_cyclic(void *arg) {
 				page_data_buf[index].size  = info->page_size;
 				memcpy(page_data_buf[index].buf, buf, info->page_size);
 			}
-unlock:
-			pthread_mutex_unlock(&page_data_buf[index].mutex);
+			page_flag_buf->index = index;
+			buf_ready = TRUE;
+next:
+			page_flag_buf->ready = FLAG_READY;
+			page_flag_buf = page_flag_buf->next;
 
 		}
-	}
 
+		pthread_mutex_unlock(&page_data_buf[index].mutex);
+	}
 	retval = NULL;
 
 fail:
@@ -7265,14 +7316,15 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
 	struct page_desc pd;
 	struct timeval tv_start;
 	struct timeval last, new;
-	unsigned long long consuming_pfn;
 	pthread_t **threads = NULL;
 	struct thread_args *kdump_thread_args = NULL;
 	void *thread_result;
-	int page_data_num;
+	int page_buf_num;
 	struct page_data *page_data_buf = NULL;
 	int i;
 	int index;
+	int end_count, consuming, check_count;
+	mdf_pfn_t current_pfn, temp_pfn;
 
 	if (info->flag_elf_dumpfile)
 		return FALSE;
@@ -7319,16 +7371,11 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
 	threads = info->threads;
 	kdump_thread_args = info->kdump_thread_args;
 
-	page_data_num = info->num_buffers;
+	page_buf_num = info->num_buffers;
 	page_data_buf = info->page_data_buf;
 
-	for (i = 0; i < page_data_num; i++) {
-		/*
-		 * producer will use pfn in page_data_buf to decide the
-		 * consumed pfn
-		 */
-		page_data_buf[i].pfn = start_pfn - 1;
-		page_data_buf[i].ready = 0;
+	for (i = 0; i < page_buf_num; i++) {
+		page_data_buf[i].used = 0;
 		res = pthread_mutex_init(&page_data_buf[i].mutex, NULL);
 		if (res != 0) {
 			ERRMSG("Can't initialize mutex of page_data_buf. %s\n",
@@ -7342,8 +7389,9 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
 		kdump_thread_args[i].len_buf_out = len_buf_out;
 		kdump_thread_args[i].start_pfn = start_pfn;
 		kdump_thread_args[i].end_pfn = end_pfn;
-		kdump_thread_args[i].page_data_num = page_data_num;
+		kdump_thread_args[i].page_buf_num = page_buf_num;
 		kdump_thread_args[i].page_data_buf = page_data_buf;
+		kdump_thread_args[i].page_flag_buf = info->page_flag_buf[i];
 		kdump_thread_args[i].cycle = cycle;
 
 		res = pthread_create(threads[i], NULL,
@@ -7356,55 +7404,94 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
 		}
 	}
 
-	consuming_pfn = start_pfn;
-	index = -1;
+	while (1) {
+		consuming = 0;
+		check_count = 0;
+		end_count = 0;
 
-	gettimeofday(&last, NULL);
+		/*
+		 * The basic idea is producer producing page and consumer writing page.
+		 * Each producer have a page_flag_buf list which is used for storing page's description.
+		 * The size of page_flag_buf is little so it won't take too much memory.
+		 * And all producers will share a page_data_buf array which is used for storing page's compressed data.
+		 * The main thread is the consumer. It will find the next pfn and write it into file.
+		 * The next pfn is smallest pfn in all page_flag_buf.
+		 */
+		while (1) {
+			current_pfn = end_pfn;
 
-	while (consuming_pfn < end_pfn) {
-		index = consuming_pfn % page_data_num;
+			/*
+			 * page_flag_buf is in circular linked list.
+			 * The array info->page_flag_buf[] records the current page_flag_buf in each thread's
+			 * page_flag_buf list.
+			 * consuming is used for recording in which thread the pfn is the smallest.
+			 * current_pfn is used for recording the value of pfn when checking the pfn.
+			 */
+			for (i = 0; i < info->num_threads; i++) {
+				if (info->page_flag_buf[i]->ready == FLAG_UNUSED)
+					continue;
+				temp_pfn = info->page_flag_buf[i]->pfn;
 
-		gettimeofday(&new, NULL);
-		if (new.tv_sec - last.tv_sec > WAIT_TIME) {
-			ERRMSG("Can't get data of pfn %llx.\n", consuming_pfn);
-			goto out;
-		}
+				/*
+				 * count how many threads have reached the end.
+				 */
+				if (temp_pfn >= end_pfn) {
+					end_count++;
+					info->page_flag_buf[i]->ready = FLAG_UNUSED;
+					continue;
+				}
 
-		/*
-		 * check pfn first without mutex locked to reduce the time
-		 * trying to lock the mutex
-		 */
-		if (page_data_buf[index].pfn != consuming_pfn)
-			continue;
+				if (current_pfn < temp_pfn)
+					continue;
 
-		if (pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
-			continue;
+				check_count++;
+				consuming = i;
+				current_pfn = temp_pfn;
+			}
+
+			/*
+			 * If all the threads have reached the end, we will finish writing.
+			 */
+			if (end_count >= info->num_threads)
+				goto finish;
+
+			/*
+			 * Since it has the probabilty that there is no page_flag_buf being ready,
+			 * we should recheck if it happens.
+			 */
+			if (check_count == 0)
+				continue;
+
+			/*
+			 * When we check the pfn in page_flag_buf, it may be being produced.
+			 * So we should wait until it is ready to use. And if the pfn is
+			 * different from the value when we check, we should rechoose the buf.
+			 */
+			gettimeofday(&last, NULL);
+			while (info->page_flag_buf[consuming]->ready != FLAG_READY) {
+				gettimeofday(&new, NULL);
+				if (new.tv_sec - last.tv_sec > WAIT_TIME) {
+					ERRMSG("Can't get data of pfn.\n");
+					goto out;
+				}
+			}
 
-		/* check whether the found one is ready to be consumed */
-		if (page_data_buf[index].pfn != consuming_pfn ||
-		    page_data_buf[index].ready != 1) {
-			goto unlock;
+			if (current_pfn == info->page_flag_buf[consuming]->pfn)
+				break;
 		}
 
 		if ((num_dumped % per) == 0)
 			print_progress(PROGRESS_COPY, num_dumped, info->num_dumpable);
 
-		/* next pfn is found, refresh last here */
-		last = new;
-		consuming_pfn++;
-		info->consumed_pfn++;
-		page_data_buf[index].ready = 0;
-
-		if (page_data_buf[index].dumpable == FALSE)
-			goto unlock;
-
 		num_dumped++;
 
-		if (page_data_buf[index].zero == TRUE) {
+
+		if (info->page_flag_buf[consuming]->zero == TRUE) {
 			if (!write_cache(cd_header, pd_zero, sizeof(page_desc_t)))
 				goto out;
 			pfn_zero++;
 		} else {
+			index = info->page_flag_buf[consuming]->index;
 			pd.flags      = page_data_buf[index].flags;
 			pd.size       = page_data_buf[index].size;
 			pd.page_flags = 0;
@@ -7420,12 +7507,12 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
 			 */
 			if (!write_cache(cd_page, page_data_buf[index].buf, pd.size))
 				goto out;
-
+			page_data_buf[index].used = 0;
 		}
-unlock:
-		pthread_mutex_unlock(&page_data_buf[index].mutex);
+		info->page_flag_buf[consuming]->ready = FLAG_UNUSED;
+		info->page_flag_buf[consuming] = info->page_flag_buf[consuming]->next;
 	}
-
+finish:
 	ret = TRUE;
 	/*
 	 * print [100 %]
@@ -7464,7 +7551,7 @@ out:
 	}
 
 	if (page_data_buf != NULL) {
-		for (i = 0; i < page_data_num; i++) {
+		for (i = 0; i < page_buf_num; i++) {
 			pthread_mutex_destroy(&page_data_buf[i].mutex);
 		}
 	}
@@ -7564,6 +7651,7 @@ write_kdump_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_pag
 		num_dumped++;
 		if (!read_pfn(pfn, buf))
 			goto out;
+
 		filter_data_buffer(buf, pfn_to_paddr(pfn), info->page_size);
 
 		/*
diff --git a/makedumpfile.h b/makedumpfile.h
index e0b5bbf..8a9a5b2 100644
--- a/makedumpfile.h
+++ b/makedumpfile.h
@@ -977,7 +977,7 @@ typedef unsigned long long int ulonglong;
 #define PAGE_DATA_NUM	(50)
 #define WAIT_TIME	(60 * 10)
 #define PTHREAD_FAIL	((void *)-2)
-#define NUM_BUFFERS	(50)
+#define NUM_BUFFERS	(20)
 
 struct mmap_cache {
 	char	*mmap_buf;
@@ -985,28 +985,36 @@ struct mmap_cache {
 	off_t   mmap_end_offset;
 };
 
+enum {
+	FLAG_UNUSED,
+	FLAG_READY,
+	FLAG_FILLING
+};
+struct page_flag {
+	mdf_pfn_t pfn;
+	char zero;
+	char ready;
+	short index;
+	struct page_flag *next;
+};
+
 struct page_data
 {
-	mdf_pfn_t pfn;
-	int dumpable;
-	int zero;
-	unsigned int flags;
+	pthread_mutex_t mutex;
 	long size;
 	unsigned char *buf;
-	pthread_mutex_t mutex;
-	/*
-	 * whether the page_data is ready to be consumed
-	 */
-	int ready;
+	int flags;
+	int used;
 };
 
 struct thread_args {
 	int thread_num;
 	unsigned long len_buf_out;
 	mdf_pfn_t start_pfn, end_pfn;
-	int page_data_num;
+	int page_buf_num;
 	struct cycle *cycle;
 	struct page_data *page_data_buf;
+	struct page_flag *page_flag_buf;
 };
 
 /*
@@ -1295,6 +1303,7 @@ struct DumpInfo {
 	pthread_t **threads;
 	struct thread_args *kdump_thread_args;
 	struct page_data *page_data_buf;
+	struct page_flag **page_flag_buf;
 	pthread_rwlock_t usemmap_rwlock;
 	mdf_pfn_t current_pfn;
 	pthread_mutex_t current_pfn_mutex;
-- 
1.8.3.1




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Re: [PATCH v1] Improve the performance of --num-threads -d 31

[Minoru Usui]

Hi, Zhou

I have some comments.
I'm sorry if I have misunderstood your code.

> -----Original Message-----
> From: kexec [mailto:kexec-bounces@lists.infradead.org] On Behalf Of Zhou Wenjian
> Sent: Monday, February 01, 2016 3:22 PM
> To: kexec@lists.infradead.org
> Subject: [PATCH v1] Improve the performance of --num-threads -d 31
> 
> v1:
>         1. change page_flag.ready's value to enum
>         2. change the patch description
>         3. cleanup some codes
> 	4. fix a bug in cyclic mode
> 
> multi-threads implementation will introduce extra cost when handling
> each page. The origin implementation will also do the extra work for
> filtered pages. So there is a big performance degradation in
> --num-threads -d 31.
> The new implementation won't do the extra work for filtered pages any
> more. So the performance of -d 31 is close to that of serial processing.
> 
> The new implementation is just like the following:
>         * The basic idea is producer producing page and consumer writing page.
>         * Each producer have a page_flag_buf list which is used for storing
>           page's description.
>         * The size of page_flag_buf is little so it won't take too much memory.
>         * And all producers will share a page_data_buf array which is
>           used for storing page's compressed data.
>         * The main thread is the consumer. It will find the next pfn and write
>           it into file.
>         * The next pfn is smallest pfn in all page_flag_buf.
> 
> Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>
> ---
>  makedumpfile.c | 258 ++++++++++++++++++++++++++++++++++++++-------------------
>  makedumpfile.h |  31 ++++---
>  2 files changed, 193 insertions(+), 96 deletions(-)
> 
> diff --git a/makedumpfile.c b/makedumpfile.c
> index fa0b779..0ecd065 100644
> --- a/makedumpfile.c
> +++ b/makedumpfile.c
> @@ -3483,7 +3483,8 @@ initial_for_parallel()
>  	unsigned long page_data_buf_size;
>  	unsigned long limit_size;
>  	int page_data_num;
> -	int i;
> +	struct page_flag *current;
> +	int i, j;
> 
>  	len_buf_out = calculate_len_buf_out(info->page_size);
> 
> @@ -3562,8 +3563,10 @@ initial_for_parallel()
>  		      - MAP_REGION * info->num_threads) * 0.6;
> 
>  	page_data_num = limit_size / page_data_buf_size;
> +	info->num_buffers = 3 * info->num_threads;
> 
> -	info->num_buffers = MIN(NUM_BUFFERS, page_data_num);
> +	info->num_buffers = MAX(info->num_buffers, NUM_BUFFERS);
> +	info->num_buffers = MIN(info->num_buffers, page_data_num);
> 
>  	DEBUG_MSG("Number of struct page_data for produce/consume: %d\n",
>  			info->num_buffers);
> @@ -3588,6 +3591,36 @@ initial_for_parallel()
>  	}
> 
>  	/*
> +	 * initial page_flag for each thread
> +	 */
> +	if ((info->page_flag_buf = malloc(sizeof(void *) * info->num_threads))
> +	    == NULL) {
> +		MSG("Can't allocate memory for page_flag_buf. %s\n",
> +				strerror(errno));
> +		return FALSE;
> +	}
> +	memset(info->page_flag_buf, 0, sizeof(void *) * info->num_threads);
> +
> +	for (i = 0; i < info->num_threads; i++) {
> +		if ((info->page_flag_buf[i] = malloc(sizeof(struct page_flag))) == NULL) {

Fist element of struct page_flag in circular list is allocated by malloc(), 
but other elements are allocated by calloc().(see below)
I think both elements should be allocated by calloc().

> +			MSG("Can't allocate memory for page_flag_buf. %s\n",
> +				strerror(errno));
> +			return FALSE;
> +		}
> +		current = info->page_flag_buf[i];
> +
> +		for (j = 1; j < NUM_BUFFERS; j++) {
> +			if ((current->next = calloc(0, sizeof(struct page_flag))) == NULL) {
> +				MSG("Can't allocate memory for data of page_data_buf. %s\n",
> +					strerror(errno));
> +				return FALSE;
> +			}


First argument of calloc() should be 1, not 0.
And there is typo in error message.
Allocated element is not page_data_buf.

> +			current = current->next;
> +		}
> +		current->next = info->page_flag_buf[i];
> +	}
> +
> +	/*
>  	 * initial fd_memory for threads
>  	 */
>  	for (i = 0; i < info->num_threads; i++) {
> @@ -3612,7 +3645,8 @@ initial_for_parallel()
>  void
>  free_for_parallel()
>  {
> -	int i;
> +	int i, j;
> +	struct page_flag *current;
> 
>  	if (info->threads != NULL) {
>  		for (i = 0; i < info->num_threads; i++) {
> @@ -3655,6 +3689,19 @@ free_for_parallel()
>  		free(info->page_data_buf);
>  	}
> 
> +	if (info->page_flag_buf != NULL) {
> +		for (i = 0; i < info->num_threads; i++) {
> +			for (j = 0; j < NUM_BUFFERS; j++) {
> +				if (info->page_flag_buf[i] != NULL) {
> +					current = info->page_flag_buf[i];
> +					info->page_flag_buf[i] = current->next;
> +					free(current);
> +				}
> +			}
> +		}
> +		free(info->page_flag_buf);
> +	}
> +
>  	if (info->parallel_info == NULL)
>  		return;
> 
> @@ -7076,10 +7123,10 @@ kdump_thread_function_cyclic(void *arg) {
>  	void *retval = PTHREAD_FAIL;
>  	struct thread_args *kdump_thread_args = (struct thread_args *)arg;
>  	struct page_data *page_data_buf = kdump_thread_args->page_data_buf;
> +	struct page_flag *page_flag_buf = kdump_thread_args->page_flag_buf;
>  	struct cycle *cycle = kdump_thread_args->cycle;
> -	int page_data_num = kdump_thread_args->page_data_num;
>  	mdf_pfn_t pfn;
> -	int index;
> +	int index = kdump_thread_args->thread_num;
>  	int buf_ready;
>  	int dumpable;
>  	int fd_memory = 0;
> @@ -7125,47 +7172,47 @@ kdump_thread_function_cyclic(void *arg) {
>  						kdump_thread_args->thread_num);
>  	}
> 
> -	while (1) {
> -		/* get next pfn */
> -		pthread_mutex_lock(&info->current_pfn_mutex);
> -		pfn = info->current_pfn;
> -		info->current_pfn++;
> -		pthread_mutex_unlock(&info->current_pfn_mutex);
> +	/*
> +	 * filtered page won't take anything
> +	 * unfiltered zero page will only take a page_flag_buf
> +	 * unfiltered non-zero page will take a page_flag_buf and a page_data_buf
> +	 */
> +	while (page_flag_buf->pfn < kdump_thread_args->end_pfn) {

At first, page_flag_buf->pfn is not initialized.
I think this block should be replaced with the following code.

===
  do {
    :
  } while(page_flag_buf->pfn < kdump_thread_args->end_pfn)
===

> +		buf_ready = FALSE;
> 
> -		if (pfn >= kdump_thread_args->end_pfn)
> -			break;
> +		while (page_data_buf[index].used != 0 ||
> +				pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
> +			index = (index + 1) % info->num_buffers;
> 
> -		index = -1;
> -		buf_ready = FALSE;
> +		page_data_buf[index].used = 1;

"1" is a magic number.
It should be changed TRUE or FALSE.

>  		while (buf_ready == FALSE) {
>  			pthread_testcancel();
> -
> -			index = pfn % page_data_num;
> -
> -			if (pfn - info->consumed_pfn > info->num_buffers)
> +			if (page_flag_buf->ready == FLAG_READY)
>  				continue;

At first, page_flag_buf->ready is uninitialized, too.
Should it be initialized in head part of this function, even if FLAG_UNUSED is defined 0?


> 
> -			if (page_data_buf[index].ready != 0)
> -				continue;
> -
> -			pthread_mutex_lock(&page_data_buf[index].mutex);
> +			/* get next pfn */
> +			pthread_mutex_lock(&info->current_pfn_mutex);
> +			pfn = info->current_pfn;
> +			info->current_pfn++;
> +			page_flag_buf->ready = FLAG_FILLING;
> +			pthread_mutex_unlock(&info->current_pfn_mutex);
> 
> -			if (page_data_buf[index].ready != 0)
> -				goto unlock;
> +			page_flag_buf->pfn = pfn;

It set FLAG_FILLING to page_flag_buf->ready before setting pfn to page_flag_buf->pfn.
But consumer gets page_flag_buf->pfn after checking page_flag_buf->ready != FLAG_UNUSED
in getting minimum pfn of each thread block.
Should it set page_flag_buf->pfn first?

> 
> -			buf_ready = TRUE;
> -
> -			page_data_buf[index].pfn = pfn;
> -			page_data_buf[index].ready = 1;
> +			if (pfn >= kdump_thread_args->end_pfn) {
> +				page_data_buf[index].used = 0;
> +				page_flag_buf->ready = FLAG_READY;
> +				info->current_pfn--;
> +				break;
> +			}

This block decrements info->current_pfn without info->current_pfn_mutex.
I think this block should be moved into previous pthread_mutex_lock(info->current_pfn_mutex) block, so it can remove.

> 
>  			dumpable = is_dumpable(
>  				info->fd_bitmap ? &bitmap_parallel : info->bitmap2,
>  				pfn,
>  				cycle);
> -			page_data_buf[index].dumpable = dumpable;
>  			if (!dumpable)
> -				goto unlock;
> +				continue;
> 
>  			if (!read_pfn_parallel(fd_memory, pfn, buf,
>  					       &bitmap_memory_parallel,
> @@ -7178,11 +7225,11 @@ kdump_thread_function_cyclic(void *arg) {
> 
>  			if ((info->dump_level & DL_EXCLUDE_ZERO)
>  			    && is_zero_page(buf, info->page_size)) {
> -				page_data_buf[index].zero = TRUE;
> -				goto unlock;
> +				page_flag_buf->zero = TRUE;
> +				goto next;
>  			}

First, this code gets page_data_buf, then it gets page_flag_buf.
However, if processed pfn is zero page, 
it processes next pfn while keeping page_data_buf.

I think it should get page_flag_buf, then get page_data_buf
in order to shorten the holding period of the page_data_buf[index].mutex.

Thanks,
Minoru Usui

> 
> -			page_data_buf[index].zero = FALSE;
> +			page_flag_buf->zero = FALSE;
> 
>  			/*
>  			 * Compress the page data.
> @@ -7232,12 +7279,16 @@ kdump_thread_function_cyclic(void *arg) {
>  				page_data_buf[index].size  = info->page_size;
>  				memcpy(page_data_buf[index].buf, buf, info->page_size);
>  			}
> -unlock:
> -			pthread_mutex_unlock(&page_data_buf[index].mutex);
> +			page_flag_buf->index = index;
> +			buf_ready = TRUE;
> +next:
> +			page_flag_buf->ready = FLAG_READY;
> +			page_flag_buf = page_flag_buf->next;
> 
>  		}
> -	}
> 
> +		pthread_mutex_unlock(&page_data_buf[index].mutex);
> +	}
>  	retval = NULL;
> 
>  fail:
> @@ -7265,14 +7316,15 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>  	struct page_desc pd;
>  	struct timeval tv_start;
>  	struct timeval last, new;
> -	unsigned long long consuming_pfn;
>  	pthread_t **threads = NULL;
>  	struct thread_args *kdump_thread_args = NULL;
>  	void *thread_result;
> -	int page_data_num;
> +	int page_buf_num;
>  	struct page_data *page_data_buf = NULL;
>  	int i;
>  	int index;
> +	int end_count, consuming, check_count;
> +	mdf_pfn_t current_pfn, temp_pfn;
> 
>  	if (info->flag_elf_dumpfile)
>  		return FALSE;
> @@ -7319,16 +7371,11 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>  	threads = info->threads;
>  	kdump_thread_args = info->kdump_thread_args;
> 
> -	page_data_num = info->num_buffers;
> +	page_buf_num = info->num_buffers;
>  	page_data_buf = info->page_data_buf;
> 
> -	for (i = 0; i < page_data_num; i++) {
> -		/*
> -		 * producer will use pfn in page_data_buf to decide the
> -		 * consumed pfn
> -		 */
> -		page_data_buf[i].pfn = start_pfn - 1;
> -		page_data_buf[i].ready = 0;
> +	for (i = 0; i < page_buf_num; i++) {
> +		page_data_buf[i].used = 0;
>  		res = pthread_mutex_init(&page_data_buf[i].mutex, NULL);
>  		if (res != 0) {
>  			ERRMSG("Can't initialize mutex of page_data_buf. %s\n",
> @@ -7342,8 +7389,9 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>  		kdump_thread_args[i].len_buf_out = len_buf_out;
>  		kdump_thread_args[i].start_pfn = start_pfn;
>  		kdump_thread_args[i].end_pfn = end_pfn;
> -		kdump_thread_args[i].page_data_num = page_data_num;
> +		kdump_thread_args[i].page_buf_num = page_buf_num;
>  		kdump_thread_args[i].page_data_buf = page_data_buf;
> +		kdump_thread_args[i].page_flag_buf = info->page_flag_buf[i];
>  		kdump_thread_args[i].cycle = cycle;
> 
>  		res = pthread_create(threads[i], NULL,
> @@ -7356,55 +7404,94 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>  		}
>  	}
> 
> -	consuming_pfn = start_pfn;
> -	index = -1;
> +	while (1) {
> +		consuming = 0;
> +		check_count = 0;
> +		end_count = 0;
> 
> -	gettimeofday(&last, NULL);
> +		/*
> +		 * The basic idea is producer producing page and consumer writing page.
> +		 * Each producer have a page_flag_buf list which is used for storing page's description.
> +		 * The size of page_flag_buf is little so it won't take too much memory.
> +		 * And all producers will share a page_data_buf array which is used for storing page's compressed data.
> +		 * The main thread is the consumer. It will find the next pfn and write it into file.
> +		 * The next pfn is smallest pfn in all page_flag_buf.
> +		 */
> +		while (1) {
> +			current_pfn = end_pfn;
> 
> -	while (consuming_pfn < end_pfn) {
> -		index = consuming_pfn % page_data_num;
> +			/*
> +			 * page_flag_buf is in circular linked list.
> +			 * The array info->page_flag_buf[] records the current page_flag_buf in each thread's
> +			 * page_flag_buf list.
> +			 * consuming is used for recording in which thread the pfn is the smallest.
> +			 * current_pfn is used for recording the value of pfn when checking the pfn.
> +			 */
> +			for (i = 0; i < info->num_threads; i++) {
> +				if (info->page_flag_buf[i]->ready == FLAG_UNUSED)
> +					continue;
> +				temp_pfn = info->page_flag_buf[i]->pfn;
> 
> -		gettimeofday(&new, NULL);
> -		if (new.tv_sec - last.tv_sec > WAIT_TIME) {
> -			ERRMSG("Can't get data of pfn %llx.\n", consuming_pfn);
> -			goto out;
> -		}
> +				/*
> +				 * count how many threads have reached the end.
> +				 */
> +				if (temp_pfn >= end_pfn) {
> +					end_count++;
> +					info->page_flag_buf[i]->ready = FLAG_UNUSED;
> +					continue;
> +				}
> 
> -		/*
> -		 * check pfn first without mutex locked to reduce the time
> -		 * trying to lock the mutex
> -		 */
> -		if (page_data_buf[index].pfn != consuming_pfn)
> -			continue;
> +				if (current_pfn < temp_pfn)
> +					continue;
> 
> -		if (pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
> -			continue;
> +				check_count++;
> +				consuming = i;
> +				current_pfn = temp_pfn;
> +			}
> +
> +			/*
> +			 * If all the threads have reached the end, we will finish writing.
> +			 */
> +			if (end_count >= info->num_threads)
> +				goto finish;
> +
> +			/*
> +			 * Since it has the probabilty that there is no page_flag_buf being ready,
> +			 * we should recheck if it happens.
> +			 */
> +			if (check_count == 0)
> +				continue;
> +
> +			/*
> +			 * When we check the pfn in page_flag_buf, it may be being produced.
> +			 * So we should wait until it is ready to use. And if the pfn is
> +			 * different from the value when we check, we should rechoose the buf.
> +			 */
> +			gettimeofday(&last, NULL);
> +			while (info->page_flag_buf[consuming]->ready != FLAG_READY) {
> +				gettimeofday(&new, NULL);
> +				if (new.tv_sec - last.tv_sec > WAIT_TIME) {
> +					ERRMSG("Can't get data of pfn.\n");
> +					goto out;
> +				}
> +			}
> 
> -		/* check whether the found one is ready to be consumed */
> -		if (page_data_buf[index].pfn != consuming_pfn ||
> -		    page_data_buf[index].ready != 1) {
> -			goto unlock;
> +			if (current_pfn == info->page_flag_buf[consuming]->pfn)
> +				break;
>  		}
> 
>  		if ((num_dumped % per) == 0)
>  			print_progress(PROGRESS_COPY, num_dumped, info->num_dumpable);
> 
> -		/* next pfn is found, refresh last here */
> -		last = new;
> -		consuming_pfn++;
> -		info->consumed_pfn++;
> -		page_data_buf[index].ready = 0;
> -
> -		if (page_data_buf[index].dumpable == FALSE)
> -			goto unlock;
> -
>  		num_dumped++;
> 
> -		if (page_data_buf[index].zero == TRUE) {
> +
> +		if (info->page_flag_buf[consuming]->zero == TRUE) {
>  			if (!write_cache(cd_header, pd_zero, sizeof(page_desc_t)))
>  				goto out;
>  			pfn_zero++;
>  		} else {
> +			index = info->page_flag_buf[consuming]->index;
>  			pd.flags      = page_data_buf[index].flags;
>  			pd.size       = page_data_buf[index].size;
>  			pd.page_flags = 0;
> @@ -7420,12 +7507,12 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>  			 */
>  			if (!write_cache(cd_page, page_data_buf[index].buf, pd.size))
>  				goto out;
> -
> +			page_data_buf[index].used = 0;
>  		}
> -unlock:
> -		pthread_mutex_unlock(&page_data_buf[index].mutex);
> +		info->page_flag_buf[consuming]->ready = FLAG_UNUSED;
> +		info->page_flag_buf[consuming] = info->page_flag_buf[consuming]->next;
>  	}
> -
> +finish:
>  	ret = TRUE;
>  	/*
>  	 * print [100 %]
> @@ -7464,7 +7551,7 @@ out:
>  	}
> 
>  	if (page_data_buf != NULL) {
> -		for (i = 0; i < page_data_num; i++) {
> +		for (i = 0; i < page_buf_num; i++) {
>  			pthread_mutex_destroy(&page_data_buf[i].mutex);
>  		}
>  	}
> @@ -7564,6 +7651,7 @@ write_kdump_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_pag
>  		num_dumped++;
>  		if (!read_pfn(pfn, buf))
>  			goto out;
> +
>  		filter_data_buffer(buf, pfn_to_paddr(pfn), info->page_size);
> 
>  		/*
> diff --git a/makedumpfile.h b/makedumpfile.h
> index e0b5bbf..8a9a5b2 100644
> --- a/makedumpfile.h
> +++ b/makedumpfile.h
> @@ -977,7 +977,7 @@ typedef unsigned long long int ulonglong;
>  #define PAGE_DATA_NUM	(50)
>  #define WAIT_TIME	(60 * 10)
>  #define PTHREAD_FAIL	((void *)-2)
> -#define NUM_BUFFERS	(50)
> +#define NUM_BUFFERS	(20)
> 
>  struct mmap_cache {
>  	char	*mmap_buf;
> @@ -985,28 +985,36 @@ struct mmap_cache {
>  	off_t   mmap_end_offset;
>  };
> 
> +enum {
> +	FLAG_UNUSED,
> +	FLAG_READY,
> +	FLAG_FILLING
> +};
> +struct page_flag {
> +	mdf_pfn_t pfn;
> +	char zero;
> +	char ready;
> +	short index;
> +	struct page_flag *next;
> +};
> +
>  struct page_data
>  {
> -	mdf_pfn_t pfn;
> -	int dumpable;
> -	int zero;
> -	unsigned int flags;
> +	pthread_mutex_t mutex;
>  	long size;
>  	unsigned char *buf;
> -	pthread_mutex_t mutex;
> -	/*
> -	 * whether the page_data is ready to be consumed
> -	 */
> -	int ready;
> +	int flags;
> +	int used;
>  };
> 
>  struct thread_args {
>  	int thread_num;
>  	unsigned long len_buf_out;
>  	mdf_pfn_t start_pfn, end_pfn;
> -	int page_data_num;
> +	int page_buf_num;
>  	struct cycle *cycle;
>  	struct page_data *page_data_buf;
> +	struct page_flag *page_flag_buf;
>  };
> 
>  /*
> @@ -1295,6 +1303,7 @@ struct DumpInfo {
>  	pthread_t **threads;
>  	struct thread_args *kdump_thread_args;
>  	struct page_data *page_data_buf;
> +	struct page_flag **page_flag_buf;
>  	pthread_rwlock_t usemmap_rwlock;
>  	mdf_pfn_t current_pfn;
>  	pthread_mutex_t current_pfn_mutex;
> --
> 1.8.3.1
> 
> 
> 
> 
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

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Re: [PATCH v1] Improve the performance of --num-threads -d 31

[Minoru Usui]

Hello,

> -----Original Message-----
> From: kexec [mailto:kexec-bounces@lists.infradead.org] On Behalf Of Minoru Usui
> Sent: Thursday, February 04, 2016 8:52 AM
> To: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>; kexec@lists.infradead.org
> Subject: Re: [PATCH v1] Improve the performance of --num-threads -d 31
> 
> Hi, Zhou
> 
> I have some comments.
> I'm sorry if I have misunderstood your code.
> 
> > -----Original Message-----
> > From: kexec [mailto:kexec-bounces@lists.infradead.org] On Behalf Of Zhou Wenjian
> > Sent: Monday, February 01, 2016 3:22 PM
> > To: kexec@lists.infradead.org
> > Subject: [PATCH v1] Improve the performance of --num-threads -d 31
> >
> > v1:
> >         1. change page_flag.ready's value to enum
> >         2. change the patch description
> >         3. cleanup some codes
> > 	4. fix a bug in cyclic mode
> >
> > multi-threads implementation will introduce extra cost when handling
> > each page. The origin implementation will also do the extra work for
> > filtered pages. So there is a big performance degradation in
> > --num-threads -d 31.
> > The new implementation won't do the extra work for filtered pages any
> > more. So the performance of -d 31 is close to that of serial processing.
> >
> > The new implementation is just like the following:
> >         * The basic idea is producer producing page and consumer writing page.
> >         * Each producer have a page_flag_buf list which is used for storing
> >           page's description.
> >         * The size of page_flag_buf is little so it won't take too much memory.
> >         * And all producers will share a page_data_buf array which is
> >           used for storing page's compressed data.
> >         * The main thread is the consumer. It will find the next pfn and write
> >           it into file.
> >         * The next pfn is smallest pfn in all page_flag_buf.
> >
> > Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>
> > ---
> >  makedumpfile.c | 258 ++++++++++++++++++++++++++++++++++++++-------------------
> >  makedumpfile.h |  31 ++++---
> >  2 files changed, 193 insertions(+), 96 deletions(-)
> >
> > diff --git a/makedumpfile.c b/makedumpfile.c
> > index fa0b779..0ecd065 100644
> > --- a/makedumpfile.c
> > +++ b/makedumpfile.c
> > @@ -3483,7 +3483,8 @@ initial_for_parallel()
> >  	unsigned long page_data_buf_size;
> >  	unsigned long limit_size;
> >  	int page_data_num;
> > -	int i;
> > +	struct page_flag *current;
> > +	int i, j;
> >
> >  	len_buf_out = calculate_len_buf_out(info->page_size);
> >
> > @@ -3562,8 +3563,10 @@ initial_for_parallel()
> >  		      - MAP_REGION * info->num_threads) * 0.6;
> >
> >  	page_data_num = limit_size / page_data_buf_size;
> > +	info->num_buffers = 3 * info->num_threads;
> >
> > -	info->num_buffers = MIN(NUM_BUFFERS, page_data_num);
> > +	info->num_buffers = MAX(info->num_buffers, NUM_BUFFERS);
> > +	info->num_buffers = MIN(info->num_buffers, page_data_num);
> >
> >  	DEBUG_MSG("Number of struct page_data for produce/consume: %d\n",
> >  			info->num_buffers);
> > @@ -3588,6 +3591,36 @@ initial_for_parallel()
> >  	}
> >
> >  	/*
> > +	 * initial page_flag for each thread
> > +	 */
> > +	if ((info->page_flag_buf = malloc(sizeof(void *) * info->num_threads))
> > +	    == NULL) {
> > +		MSG("Can't allocate memory for page_flag_buf. %s\n",
> > +				strerror(errno));
> > +		return FALSE;
> > +	}
> > +	memset(info->page_flag_buf, 0, sizeof(void *) * info->num_threads);
> > +
> > +	for (i = 0; i < info->num_threads; i++) {
> > +		if ((info->page_flag_buf[i] = malloc(sizeof(struct page_flag))) == NULL) {
> 
> Fist element of struct page_flag in circular list is allocated by malloc(),
> but other elements are allocated by calloc().(see below)
> I think both elements should be allocated by calloc().
> 
> > +			MSG("Can't allocate memory for page_flag_buf. %s\n",
> > +				strerror(errno));
> > +			return FALSE;
> > +		}
> > +		current = info->page_flag_buf[i];
> > +
> > +		for (j = 1; j < NUM_BUFFERS; j++) {
> > +			if ((current->next = calloc(0, sizeof(struct page_flag))) == NULL) {
> > +				MSG("Can't allocate memory for data of page_data_buf. %s\n",
> > +					strerror(errno));
> > +				return FALSE;
> > +			}
> 
> 
> First argument of calloc() should be 1, not 0.
> And there is typo in error message.
> Allocated element is not page_data_buf.
> 
> > +			current = current->next;
> > +		}
> > +		current->next = info->page_flag_buf[i];
> > +	}
> > +
> > +	/*
> >  	 * initial fd_memory for threads
> >  	 */
> >  	for (i = 0; i < info->num_threads; i++) {
> > @@ -3612,7 +3645,8 @@ initial_for_parallel()
> >  void
> >  free_for_parallel()
> >  {
> > -	int i;
> > +	int i, j;
> > +	struct page_flag *current;
> >
> >  	if (info->threads != NULL) {
> >  		for (i = 0; i < info->num_threads; i++) {
> > @@ -3655,6 +3689,19 @@ free_for_parallel()
> >  		free(info->page_data_buf);
> >  	}
> >
> > +	if (info->page_flag_buf != NULL) {
> > +		for (i = 0; i < info->num_threads; i++) {
> > +			for (j = 0; j < NUM_BUFFERS; j++) {
> > +				if (info->page_flag_buf[i] != NULL) {
> > +					current = info->page_flag_buf[i];
> > +					info->page_flag_buf[i] = current->next;
> > +					free(current);
> > +				}
> > +			}
> > +		}
> > +		free(info->page_flag_buf);
> > +	}
> > +
> >  	if (info->parallel_info == NULL)
> >  		return;
> >
> > @@ -7076,10 +7123,10 @@ kdump_thread_function_cyclic(void *arg) {
> >  	void *retval = PTHREAD_FAIL;
> >  	struct thread_args *kdump_thread_args = (struct thread_args *)arg;
> >  	struct page_data *page_data_buf = kdump_thread_args->page_data_buf;
> > +	struct page_flag *page_flag_buf = kdump_thread_args->page_flag_buf;
> >  	struct cycle *cycle = kdump_thread_args->cycle;
> > -	int page_data_num = kdump_thread_args->page_data_num;
> >  	mdf_pfn_t pfn;
> > -	int index;
> > +	int index = kdump_thread_args->thread_num;
> >  	int buf_ready;
> >  	int dumpable;
> >  	int fd_memory = 0;
> > @@ -7125,47 +7172,47 @@ kdump_thread_function_cyclic(void *arg) {
> >  						kdump_thread_args->thread_num);
> >  	}
> >
> > -	while (1) {
> > -		/* get next pfn */
> > -		pthread_mutex_lock(&info->current_pfn_mutex);
> > -		pfn = info->current_pfn;
> > -		info->current_pfn++;
> > -		pthread_mutex_unlock(&info->current_pfn_mutex);
> > +	/*
> > +	 * filtered page won't take anything
> > +	 * unfiltered zero page will only take a page_flag_buf
> > +	 * unfiltered non-zero page will take a page_flag_buf and a page_data_buf
> > +	 */
> > +	while (page_flag_buf->pfn < kdump_thread_args->end_pfn) {
> 
> At first, page_flag_buf->pfn is not initialized.
> I think this block should be replaced with the following code.
> 
> ===
>   do {
>     :
>   } while(page_flag_buf->pfn < kdump_thread_args->end_pfn)
> ===

I'm sorry, above suggestion is meaningless in terms of page_flag_buf->pfn is uninitialized.
It should be replaced like following.

===
  while (1) {
    :
    while (buf_ready == FALSE) {
       :
      if (pfn >= kdump_thread_args->end_pfn) {
         :
        goto finish;
      }
      :
    }
    :
  }
finish:
===

Thanks,
Minoru Usui

 
> > +		buf_ready = FALSE;
> >
> > -		if (pfn >= kdump_thread_args->end_pfn)
> > -			break;
> > +		while (page_data_buf[index].used != 0 ||
> > +				pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
> > +			index = (index + 1) % info->num_buffers;
> >
> > -		index = -1;
> > -		buf_ready = FALSE;
> > +		page_data_buf[index].used = 1;
> 
> "1" is a magic number.
> It should be changed TRUE or FALSE.
> 
> >  		while (buf_ready == FALSE) {
> >  			pthread_testcancel();
> > -
> > -			index = pfn % page_data_num;
> > -
> > -			if (pfn - info->consumed_pfn > info->num_buffers)
> > +			if (page_flag_buf->ready == FLAG_READY)
> >  				continue;
> 
> At first, page_flag_buf->ready is uninitialized, too.
> Should it be initialized in head part of this function, even if FLAG_UNUSED is defined 0?
> 
> 
> >
> > -			if (page_data_buf[index].ready != 0)
> > -				continue;
> > -
> > -			pthread_mutex_lock(&page_data_buf[index].mutex);
> > +			/* get next pfn */
> > +			pthread_mutex_lock(&info->current_pfn_mutex);
> > +			pfn = info->current_pfn;
> > +			info->current_pfn++;
> > +			page_flag_buf->ready = FLAG_FILLING;
> > +			pthread_mutex_unlock(&info->current_pfn_mutex);
> >
> > -			if (page_data_buf[index].ready != 0)
> > -				goto unlock;
> > +			page_flag_buf->pfn = pfn;
> 
> It set FLAG_FILLING to page_flag_buf->ready before setting pfn to page_flag_buf->pfn.
> But consumer gets page_flag_buf->pfn after checking page_flag_buf->ready != FLAG_UNUSED
> in getting minimum pfn of each thread block.
> Should it set page_flag_buf->pfn first?
> 
> >
> > -			buf_ready = TRUE;
> > -
> > -			page_data_buf[index].pfn = pfn;
> > -			page_data_buf[index].ready = 1;
> > +			if (pfn >= kdump_thread_args->end_pfn) {
> > +				page_data_buf[index].used = 0;
> > +				page_flag_buf->ready = FLAG_READY;
> > +				info->current_pfn--;
> > +				break;
> > +			}
> 
> This block decrements info->current_pfn without info->current_pfn_mutex.
> I think this block should be moved into previous pthread_mutex_lock(info->current_pfn_mutex) block, so it can remove.
> 
> >
> >  			dumpable = is_dumpable(
> >  				info->fd_bitmap ? &bitmap_parallel : info->bitmap2,
> >  				pfn,
> >  				cycle);
> > -			page_data_buf[index].dumpable = dumpable;
> >  			if (!dumpable)
> > -				goto unlock;
> > +				continue;
> >
> >  			if (!read_pfn_parallel(fd_memory, pfn, buf,
> >  					       &bitmap_memory_parallel,
> > @@ -7178,11 +7225,11 @@ kdump_thread_function_cyclic(void *arg) {
> >
> >  			if ((info->dump_level & DL_EXCLUDE_ZERO)
> >  			    && is_zero_page(buf, info->page_size)) {
> > -				page_data_buf[index].zero = TRUE;
> > -				goto unlock;
> > +				page_flag_buf->zero = TRUE;
> > +				goto next;
> >  			}
> 
> First, this code gets page_data_buf, then it gets page_flag_buf.
> However, if processed pfn is zero page,
> it processes next pfn while keeping page_data_buf.
> 
> I think it should get page_flag_buf, then get page_data_buf
> in order to shorten the holding period of the page_data_buf[index].mutex.
> 
> Thanks,
> Minoru Usui
> 
> >
> > -			page_data_buf[index].zero = FALSE;
> > +			page_flag_buf->zero = FALSE;
> >
> >  			/*
> >  			 * Compress the page data.
> > @@ -7232,12 +7279,16 @@ kdump_thread_function_cyclic(void *arg) {
> >  				page_data_buf[index].size  = info->page_size;
> >  				memcpy(page_data_buf[index].buf, buf, info->page_size);
> >  			}
> > -unlock:
> > -			pthread_mutex_unlock(&page_data_buf[index].mutex);
> > +			page_flag_buf->index = index;
> > +			buf_ready = TRUE;
> > +next:
> > +			page_flag_buf->ready = FLAG_READY;
> > +			page_flag_buf = page_flag_buf->next;
> >
> >  		}
> > -	}
> >
> > +		pthread_mutex_unlock(&page_data_buf[index].mutex);
> > +	}
> >  	retval = NULL;
> >
> >  fail:
> > @@ -7265,14 +7316,15 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >  	struct page_desc pd;
> >  	struct timeval tv_start;
> >  	struct timeval last, new;
> > -	unsigned long long consuming_pfn;
> >  	pthread_t **threads = NULL;
> >  	struct thread_args *kdump_thread_args = NULL;
> >  	void *thread_result;
> > -	int page_data_num;
> > +	int page_buf_num;
> >  	struct page_data *page_data_buf = NULL;
> >  	int i;
> >  	int index;
> > +	int end_count, consuming, check_count;
> > +	mdf_pfn_t current_pfn, temp_pfn;
> >
> >  	if (info->flag_elf_dumpfile)
> >  		return FALSE;
> > @@ -7319,16 +7371,11 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >  	threads = info->threads;
> >  	kdump_thread_args = info->kdump_thread_args;
> >
> > -	page_data_num = info->num_buffers;
> > +	page_buf_num = info->num_buffers;
> >  	page_data_buf = info->page_data_buf;
> >
> > -	for (i = 0; i < page_data_num; i++) {
> > -		/*
> > -		 * producer will use pfn in page_data_buf to decide the
> > -		 * consumed pfn
> > -		 */
> > -		page_data_buf[i].pfn = start_pfn - 1;
> > -		page_data_buf[i].ready = 0;
> > +	for (i = 0; i < page_buf_num; i++) {
> > +		page_data_buf[i].used = 0;
> >  		res = pthread_mutex_init(&page_data_buf[i].mutex, NULL);
> >  		if (res != 0) {
> >  			ERRMSG("Can't initialize mutex of page_data_buf. %s\n",
> > @@ -7342,8 +7389,9 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >  		kdump_thread_args[i].len_buf_out = len_buf_out;
> >  		kdump_thread_args[i].start_pfn = start_pfn;
> >  		kdump_thread_args[i].end_pfn = end_pfn;
> > -		kdump_thread_args[i].page_data_num = page_data_num;
> > +		kdump_thread_args[i].page_buf_num = page_buf_num;
> >  		kdump_thread_args[i].page_data_buf = page_data_buf;
> > +		kdump_thread_args[i].page_flag_buf = info->page_flag_buf[i];
> >  		kdump_thread_args[i].cycle = cycle;
> >
> >  		res = pthread_create(threads[i], NULL,
> > @@ -7356,55 +7404,94 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >  		}
> >  	}
> >
> > -	consuming_pfn = start_pfn;
> > -	index = -1;
> > +	while (1) {
> > +		consuming = 0;
> > +		check_count = 0;
> > +		end_count = 0;
> >
> > -	gettimeofday(&last, NULL);
> > +		/*
> > +		 * The basic idea is producer producing page and consumer writing page.
> > +		 * Each producer have a page_flag_buf list which is used for storing page's description.
> > +		 * The size of page_flag_buf is little so it won't take too much memory.
> > +		 * And all producers will share a page_data_buf array which is used for storing page's compressed data.
> > +		 * The main thread is the consumer. It will find the next pfn and write it into file.
> > +		 * The next pfn is smallest pfn in all page_flag_buf.
> > +		 */
> > +		while (1) {
> > +			current_pfn = end_pfn;
> >
> > -	while (consuming_pfn < end_pfn) {
> > -		index = consuming_pfn % page_data_num;
> > +			/*
> > +			 * page_flag_buf is in circular linked list.
> > +			 * The array info->page_flag_buf[] records the current page_flag_buf in each thread's
> > +			 * page_flag_buf list.
> > +			 * consuming is used for recording in which thread the pfn is the smallest.
> > +			 * current_pfn is used for recording the value of pfn when checking the pfn.
> > +			 */
> > +			for (i = 0; i < info->num_threads; i++) {
> > +				if (info->page_flag_buf[i]->ready == FLAG_UNUSED)
> > +					continue;
> > +				temp_pfn = info->page_flag_buf[i]->pfn;
> >
> > -		gettimeofday(&new, NULL);
> > -		if (new.tv_sec - last.tv_sec > WAIT_TIME) {
> > -			ERRMSG("Can't get data of pfn %llx.\n", consuming_pfn);
> > -			goto out;
> > -		}
> > +				/*
> > +				 * count how many threads have reached the end.
> > +				 */
> > +				if (temp_pfn >= end_pfn) {
> > +					end_count++;
> > +					info->page_flag_buf[i]->ready = FLAG_UNUSED;
> > +					continue;
> > +				}
> >
> > -		/*
> > -		 * check pfn first without mutex locked to reduce the time
> > -		 * trying to lock the mutex
> > -		 */
> > -		if (page_data_buf[index].pfn != consuming_pfn)
> > -			continue;
> > +				if (current_pfn < temp_pfn)
> > +					continue;
> >
> > -		if (pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
> > -			continue;
> > +				check_count++;
> > +				consuming = i;
> > +				current_pfn = temp_pfn;
> > +			}
> > +
> > +			/*
> > +			 * If all the threads have reached the end, we will finish writing.
> > +			 */
> > +			if (end_count >= info->num_threads)
> > +				goto finish;
> > +
> > +			/*
> > +			 * Since it has the probabilty that there is no page_flag_buf being ready,
> > +			 * we should recheck if it happens.
> > +			 */
> > +			if (check_count == 0)
> > +				continue;
> > +
> > +			/*
> > +			 * When we check the pfn in page_flag_buf, it may be being produced.
> > +			 * So we should wait until it is ready to use. And if the pfn is
> > +			 * different from the value when we check, we should rechoose the buf.
> > +			 */
> > +			gettimeofday(&last, NULL);
> > +			while (info->page_flag_buf[consuming]->ready != FLAG_READY) {
> > +				gettimeofday(&new, NULL);
> > +				if (new.tv_sec - last.tv_sec > WAIT_TIME) {
> > +					ERRMSG("Can't get data of pfn.\n");
> > +					goto out;
> > +				}
> > +			}
> >
> > -		/* check whether the found one is ready to be consumed */
> > -		if (page_data_buf[index].pfn != consuming_pfn ||
> > -		    page_data_buf[index].ready != 1) {
> > -			goto unlock;
> > +			if (current_pfn == info->page_flag_buf[consuming]->pfn)
> > +				break;
> >  		}
> >
> >  		if ((num_dumped % per) == 0)
> >  			print_progress(PROGRESS_COPY, num_dumped, info->num_dumpable);
> >
> > -		/* next pfn is found, refresh last here */
> > -		last = new;
> > -		consuming_pfn++;
> > -		info->consumed_pfn++;
> > -		page_data_buf[index].ready = 0;
> > -
> > -		if (page_data_buf[index].dumpable == FALSE)
> > -			goto unlock;
> > -
> >  		num_dumped++;
> >
> > -		if (page_data_buf[index].zero == TRUE) {
> > +
> > +		if (info->page_flag_buf[consuming]->zero == TRUE) {
> >  			if (!write_cache(cd_header, pd_zero, sizeof(page_desc_t)))
> >  				goto out;
> >  			pfn_zero++;
> >  		} else {
> > +			index = info->page_flag_buf[consuming]->index;
> >  			pd.flags      = page_data_buf[index].flags;
> >  			pd.size       = page_data_buf[index].size;
> >  			pd.page_flags = 0;
> > @@ -7420,12 +7507,12 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >  			 */
> >  			if (!write_cache(cd_page, page_data_buf[index].buf, pd.size))
> >  				goto out;
> > -
> > +			page_data_buf[index].used = 0;
> >  		}
> > -unlock:
> > -		pthread_mutex_unlock(&page_data_buf[index].mutex);
> > +		info->page_flag_buf[consuming]->ready = FLAG_UNUSED;
> > +		info->page_flag_buf[consuming] = info->page_flag_buf[consuming]->next;
> >  	}
> > -
> > +finish:
> >  	ret = TRUE;
> >  	/*
> >  	 * print [100 %]
> > @@ -7464,7 +7551,7 @@ out:
> >  	}
> >
> >  	if (page_data_buf != NULL) {
> > -		for (i = 0; i < page_data_num; i++) {
> > +		for (i = 0; i < page_buf_num; i++) {
> >  			pthread_mutex_destroy(&page_data_buf[i].mutex);
> >  		}
> >  	}
> > @@ -7564,6 +7651,7 @@ write_kdump_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_pag
> >  		num_dumped++;
> >  		if (!read_pfn(pfn, buf))
> >  			goto out;
> > +
> >  		filter_data_buffer(buf, pfn_to_paddr(pfn), info->page_size);
> >
> >  		/*
> > diff --git a/makedumpfile.h b/makedumpfile.h
> > index e0b5bbf..8a9a5b2 100644
> > --- a/makedumpfile.h
> > +++ b/makedumpfile.h
> > @@ -977,7 +977,7 @@ typedef unsigned long long int ulonglong;
> >  #define PAGE_DATA_NUM	(50)
> >  #define WAIT_TIME	(60 * 10)
> >  #define PTHREAD_FAIL	((void *)-2)
> > -#define NUM_BUFFERS	(50)
> > +#define NUM_BUFFERS	(20)
> >
> >  struct mmap_cache {
> >  	char	*mmap_buf;
> > @@ -985,28 +985,36 @@ struct mmap_cache {
> >  	off_t   mmap_end_offset;
> >  };
> >
> > +enum {
> > +	FLAG_UNUSED,
> > +	FLAG_READY,
> > +	FLAG_FILLING
> > +};
> > +struct page_flag {
> > +	mdf_pfn_t pfn;
> > +	char zero;
> > +	char ready;
> > +	short index;
> > +	struct page_flag *next;
> > +};
> > +
> >  struct page_data
> >  {
> > -	mdf_pfn_t pfn;
> > -	int dumpable;
> > -	int zero;
> > -	unsigned int flags;
> > +	pthread_mutex_t mutex;
> >  	long size;
> >  	unsigned char *buf;
> > -	pthread_mutex_t mutex;
> > -	/*
> > -	 * whether the page_data is ready to be consumed
> > -	 */
> > -	int ready;
> > +	int flags;
> > +	int used;
> >  };
> >
> >  struct thread_args {
> >  	int thread_num;
> >  	unsigned long len_buf_out;
> >  	mdf_pfn_t start_pfn, end_pfn;
> > -	int page_data_num;
> > +	int page_buf_num;
> >  	struct cycle *cycle;
> >  	struct page_data *page_data_buf;
> > +	struct page_flag *page_flag_buf;
> >  };
> >
> >  /*
> > @@ -1295,6 +1303,7 @@ struct DumpInfo {
> >  	pthread_t **threads;
> >  	struct thread_args *kdump_thread_args;
> >  	struct page_data *page_data_buf;
> > +	struct page_flag **page_flag_buf;
> >  	pthread_rwlock_t usemmap_rwlock;
> >  	mdf_pfn_t current_pfn;
> >  	pthread_mutex_t current_pfn_mutex;
> > --
> > 1.8.3.1
> >
> >
> >
> >
> > _______________________________________________
> > kexec mailing list
> > kexec@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
> 
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

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Re: [PATCH v1] Improve the performance of --num-threads -d 31

["Zhou, Wenjian/周文剑"]

Hello Usui,

Thanks very much for your comments.
And sorry for the late reply.

See below.

On 02/08/2016 01:00 PM, Minoru Usui wrote:
> Hello,
>
>> -----Original Message-----
>> From: kexec [mailto:kexec-bounces@lists.infradead.org] On Behalf Of Minoru Usui
>> Sent: Thursday, February 04, 2016 8:52 AM
>> To: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>; kexec@lists.infradead.org
>> Subject: Re: [PATCH v1] Improve the performance of --num-threads -d 31
>>
>> Hi, Zhou
>>
>> I have some comments.
>> I'm sorry if I have misunderstood your code.
>>
>>> -----Original Message-----
>>> From: kexec [mailto:kexec-bounces@lists.infradead.org] On Behalf Of Zhou Wenjian
>>> Sent: Monday, February 01, 2016 3:22 PM
>>> To: kexec@lists.infradead.org
>>> Subject: [PATCH v1] Improve the performance of --num-threads -d 31
>>>
>>> v1:
>>>          1. change page_flag.ready's value to enum
>>>          2. change the patch description
>>>          3. cleanup some codes
>>> 	4. fix a bug in cyclic mode
>>>
>>> multi-threads implementation will introduce extra cost when handling
>>> each page. The origin implementation will also do the extra work for
>>> filtered pages. So there is a big performance degradation in
>>> --num-threads -d 31.
>>> The new implementation won't do the extra work for filtered pages any
>>> more. So the performance of -d 31 is close to that of serial processing.
>>>
>>> The new implementation is just like the following:
>>>          * The basic idea is producer producing page and consumer writing page.
>>>          * Each producer have a page_flag_buf list which is used for storing
>>>            page's description.
>>>          * The size of page_flag_buf is little so it won't take too much memory.
>>>          * And all producers will share a page_data_buf array which is
>>>            used for storing page's compressed data.
>>>          * The main thread is the consumer. It will find the next pfn and write
>>>            it into file.
>>>          * The next pfn is smallest pfn in all page_flag_buf.
>>>
>>> Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>
>>> ---
>>>   makedumpfile.c | 258 ++++++++++++++++++++++++++++++++++++++-------------------
>>>   makedumpfile.h |  31 ++++---
>>>   2 files changed, 193 insertions(+), 96 deletions(-)
>>>
>>> diff --git a/makedumpfile.c b/makedumpfile.c
>>> index fa0b779..0ecd065 100644
>>> --- a/makedumpfile.c
>>> +++ b/makedumpfile.c
>>> @@ -3483,7 +3483,8 @@ initial_for_parallel()
>>>   	unsigned long page_data_buf_size;
>>>   	unsigned long limit_size;
>>>   	int page_data_num;
>>> -	int i;
>>> +	struct page_flag *current;
>>> +	int i, j;
>>>
>>>   	len_buf_out = calculate_len_buf_out(info->page_size);
>>>
>>> @@ -3562,8 +3563,10 @@ initial_for_parallel()
>>>   		      - MAP_REGION * info->num_threads) * 0.6;
>>>
>>>   	page_data_num = limit_size / page_data_buf_size;
>>> +	info->num_buffers = 3 * info->num_threads;
>>>
>>> -	info->num_buffers = MIN(NUM_BUFFERS, page_data_num);
>>> +	info->num_buffers = MAX(info->num_buffers, NUM_BUFFERS);
>>> +	info->num_buffers = MIN(info->num_buffers, page_data_num);
>>>
>>>   	DEBUG_MSG("Number of struct page_data for produce/consume: %d\n",
>>>   			info->num_buffers);
>>> @@ -3588,6 +3591,36 @@ initial_for_parallel()
>>>   	}
>>>
>>>   	/*
>>> +	 * initial page_flag for each thread
>>> +	 */
>>> +	if ((info->page_flag_buf = malloc(sizeof(void *) * info->num_threads))
>>> +	    == NULL) {
>>> +		MSG("Can't allocate memory for page_flag_buf. %s\n",
>>> +				strerror(errno));
>>> +		return FALSE;
>>> +	}
>>> +	memset(info->page_flag_buf, 0, sizeof(void *) * info->num_threads);
>>> +
>>> +	for (i = 0; i < info->num_threads; i++) {
>>> +		if ((info->page_flag_buf[i] = malloc(sizeof(struct page_flag))) == NULL) {
>>
>> Fist element of struct page_flag in circular list is allocated by malloc(),
>> but other elements are allocated by calloc().(see below)
>> I think both elements should be allocated by calloc().
>>

Yes, you are right.
I have made a mistake.

>>> +			MSG("Can't allocate memory for page_flag_buf. %s\n",
>>> +				strerror(errno));
>>> +			return FALSE;
>>> +		}
>>> +		current = info->page_flag_buf[i];
>>> +
>>> +		for (j = 1; j < NUM_BUFFERS; j++) {
>>> +			if ((current->next = calloc(0, sizeof(struct page_flag))) == NULL) {
>>> +				MSG("Can't allocate memory for data of page_data_buf. %s\n",
>>> +					strerror(errno));
>>> +				return FALSE;
>>> +			}
>>
>>
>> First argument of calloc() should be 1, not 0.
>> And there is typo in error message.
>> Allocated element is not page_data_buf.
>>

I agree.

>>> +			current = current->next;
>>> +		}
>>> +		current->next = info->page_flag_buf[i];
>>> +	}
>>> +
>>> +	/*
>>>   	 * initial fd_memory for threads
>>>   	 */
>>>   	for (i = 0; i < info->num_threads; i++) {
>>> @@ -3612,7 +3645,8 @@ initial_for_parallel()
>>>   void
>>>   free_for_parallel()
>>>   {
>>> -	int i;
>>> +	int i, j;
>>> +	struct page_flag *current;
>>>
>>>   	if (info->threads != NULL) {
>>>   		for (i = 0; i < info->num_threads; i++) {
>>> @@ -3655,6 +3689,19 @@ free_for_parallel()
>>>   		free(info->page_data_buf);
>>>   	}
>>>
>>> +	if (info->page_flag_buf != NULL) {
>>> +		for (i = 0; i < info->num_threads; i++) {
>>> +			for (j = 0; j < NUM_BUFFERS; j++) {
>>> +				if (info->page_flag_buf[i] != NULL) {
>>> +					current = info->page_flag_buf[i];
>>> +					info->page_flag_buf[i] = current->next;
>>> +					free(current);
>>> +				}
>>> +			}
>>> +		}
>>> +		free(info->page_flag_buf);
>>> +	}
>>> +
>>>   	if (info->parallel_info == NULL)
>>>   		return;
>>>
>>> @@ -7076,10 +7123,10 @@ kdump_thread_function_cyclic(void *arg) {
>>>   	void *retval = PTHREAD_FAIL;
>>>   	struct thread_args *kdump_thread_args = (struct thread_args *)arg;
>>>   	struct page_data *page_data_buf = kdump_thread_args->page_data_buf;
>>> +	struct page_flag *page_flag_buf = kdump_thread_args->page_flag_buf;
>>>   	struct cycle *cycle = kdump_thread_args->cycle;
>>> -	int page_data_num = kdump_thread_args->page_data_num;
>>>   	mdf_pfn_t pfn;
>>> -	int index;
>>> +	int index = kdump_thread_args->thread_num;
>>>   	int buf_ready;
>>>   	int dumpable;
>>>   	int fd_memory = 0;
>>> @@ -7125,47 +7172,47 @@ kdump_thread_function_cyclic(void *arg) {
>>>   						kdump_thread_args->thread_num);
>>>   	}
>>>
>>> -	while (1) {
>>> -		/* get next pfn */
>>> -		pthread_mutex_lock(&info->current_pfn_mutex);
>>> -		pfn = info->current_pfn;
>>> -		info->current_pfn++;
>>> -		pthread_mutex_unlock(&info->current_pfn_mutex);
>>> +	/*
>>> +	 * filtered page won't take anything
>>> +	 * unfiltered zero page will only take a page_flag_buf
>>> +	 * unfiltered non-zero page will take a page_flag_buf and a page_data_buf
>>> +	 */
>>> +	while (page_flag_buf->pfn < kdump_thread_args->end_pfn) {
>>
>> At first, page_flag_buf->pfn is not initialized.
>> I think this block should be replaced with the following code.
>>
>> ===
>>    do {
>>      :
>>    } while(page_flag_buf->pfn < kdump_thread_args->end_pfn)
>> ===
>
> I'm sorry, above suggestion is meaningless in terms of page_flag_buf->pfn is uninitialized.
> It should be replaced like following.
>
> ===
>    while (1) {
>      :
>      while (buf_ready == FALSE) {
>         :
>        if (pfn >= kdump_thread_args->end_pfn) {
>           :
>          goto finish;
>        }
>        :
>      }
>      :
>    }
> finish:
> ===
>

page_flag_buf is allocated by calloc().
The page_flag_buf->pfn's value is 0.
So I think it is not necessary to modify the code.

> Thanks,
> Minoru Usui
>
>
>>> +		buf_ready = FALSE;
>>>
>>> -		if (pfn >= kdump_thread_args->end_pfn)
>>> -			break;
>>> +		while (page_data_buf[index].used != 0 ||
>>> +				pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
>>> +			index = (index + 1) % info->num_buffers;
>>>
>>> -		index = -1;
>>> -		buf_ready = FALSE;
>>> +		page_data_buf[index].used = 1;
>>
>> "1" is a magic number.
>> It should be changed TRUE or FALSE.
>>

I see.

>>>   		while (buf_ready == FALSE) {
>>>   			pthread_testcancel();
>>> -
>>> -			index = pfn % page_data_num;
>>> -
>>> -			if (pfn - info->consumed_pfn > info->num_buffers)
>>> +			if (page_flag_buf->ready == FLAG_READY)
>>>   				continue;
>>
>> At first, page_flag_buf->ready is uninitialized, too.
>> Should it be initialized in head part of this function, even if FLAG_UNUSED is defined 0?
>>
>>

The same topic as the page_flag_buf is allocated by calloc().

>>>
>>> -			if (page_data_buf[index].ready != 0)
>>> -				continue;
>>> -
>>> -			pthread_mutex_lock(&page_data_buf[index].mutex);
>>> +			/* get next pfn */
>>> +			pthread_mutex_lock(&info->current_pfn_mutex);
>>> +			pfn = info->current_pfn;
>>> +			info->current_pfn++;
>>> +			page_flag_buf->ready = FLAG_FILLING;
>>> +			pthread_mutex_unlock(&info->current_pfn_mutex);
>>>
>>> -			if (page_data_buf[index].ready != 0)
>>> -				goto unlock;
>>> +			page_flag_buf->pfn = pfn;
>>
>> It set FLAG_FILLING to page_flag_buf->ready before setting pfn to page_flag_buf->pfn.
>> But consumer gets page_flag_buf->pfn after checking page_flag_buf->ready != FLAG_UNUSED
>> in getting minimum pfn of each thread block.
>> Should it set page_flag_buf->pfn first?
>>

Have you noticed the following code in the consumer?
<cut>
                         if (current_pfn == info->page_flag_buf[consuming]->pfn)
                                 break;
<cut>

The consumer will check if the pfn is changed after the page_flag_buf->ready turns to be FLAG_READY.
So it's not important whether setting page_flag_buf->pfn first or not.

In the other hand, even setting page_flag_buf->pfn first, if the pfn is not dumpable, the producer
will also reset the page_flag_buf->pfn.

>>>
>>> -			buf_ready = TRUE;
>>> -
>>> -			page_data_buf[index].pfn = pfn;
>>> -			page_data_buf[index].ready = 1;
>>> +			if (pfn >= kdump_thread_args->end_pfn) {
>>> +				page_data_buf[index].used = 0;
>>> +				page_flag_buf->ready = FLAG_READY;
>>> +				info->current_pfn--;
>>> +				break;
>>> +			}
>>
>> This block decrements info->current_pfn without info->current_pfn_mutex.
>> I think this block should be moved into previous pthread_mutex_lock(info->current_pfn_mutex) block, so it can remove.
>>

Why do you think it should have current_pfn_mutex?

If pfn >= kdump_thread_args->end_pfn, info->current_pfn will always larger than
kdump_thread_args->end_pfn. info->current_pfn-- won't affect anything.

The decrement operation is for cyclic mode.

>>>
>>>   			dumpable = is_dumpable(
>>>   				info->fd_bitmap ? &bitmap_parallel : info->bitmap2,
>>>   				pfn,
>>>   				cycle);
>>> -			page_data_buf[index].dumpable = dumpable;
>>>   			if (!dumpable)
>>> -				goto unlock;
>>> +				continue;
>>>
>>>   			if (!read_pfn_parallel(fd_memory, pfn, buf,
>>>   					       &bitmap_memory_parallel,
>>> @@ -7178,11 +7225,11 @@ kdump_thread_function_cyclic(void *arg) {
>>>
>>>   			if ((info->dump_level & DL_EXCLUDE_ZERO)
>>>   			    && is_zero_page(buf, info->page_size)) {
>>> -				page_data_buf[index].zero = TRUE;
>>> -				goto unlock;
>>> +				page_flag_buf->zero = TRUE;
>>> +				goto next;
>>>   			}
>>
>> First, this code gets page_data_buf, then it gets page_flag_buf.
>> However, if processed pfn is zero page,
>> it processes next pfn while keeping page_data_buf.
>>
>> I think it should get page_flag_buf, then get page_data_buf
>> in order to shorten the holding period of the page_data_buf[index].mutex.
>>

Do you mean the following logic?
1. get the page_flag_buf first
2. if the pfn is not zero page, then get the page_data_buf.

Think about the following case.
A producer get the page_flag_buf, and the pfn is not zero page.
It wants to get a page_data_buf, but there is no more page_data_buf.
Then ...

Since there are several page_data_bufs, it's not a problem that each producer
will always hold a page_data_buf.


Thanks again for your comments.
And I will post the next version later.

-- 
Thanks
Zhou

>> Thanks,
>> Minoru Usui
>>
>>>
>>> -			page_data_buf[index].zero = FALSE;
>>> +			page_flag_buf->zero = FALSE;
>>>
>>>   			/*
>>>   			 * Compress the page data.
>>> @@ -7232,12 +7279,16 @@ kdump_thread_function_cyclic(void *arg) {
>>>   				page_data_buf[index].size  = info->page_size;
>>>   				memcpy(page_data_buf[index].buf, buf, info->page_size);
>>>   			}
>>> -unlock:
>>> -			pthread_mutex_unlock(&page_data_buf[index].mutex);
>>> +			page_flag_buf->index = index;
>>> +			buf_ready = TRUE;
>>> +next:
>>> +			page_flag_buf->ready = FLAG_READY;
>>> +			page_flag_buf = page_flag_buf->next;
>>>
>>>   		}
>>> -	}
>>>
>>> +		pthread_mutex_unlock(&page_data_buf[index].mutex);
>>> +	}
>>>   	retval = NULL;
>>>
>>>   fail:
>>> @@ -7265,14 +7316,15 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>>>   	struct page_desc pd;
>>>   	struct timeval tv_start;
>>>   	struct timeval last, new;
>>> -	unsigned long long consuming_pfn;
>>>   	pthread_t **threads = NULL;
>>>   	struct thread_args *kdump_thread_args = NULL;
>>>   	void *thread_result;
>>> -	int page_data_num;
>>> +	int page_buf_num;
>>>   	struct page_data *page_data_buf = NULL;
>>>   	int i;
>>>   	int index;
>>> +	int end_count, consuming, check_count;
>>> +	mdf_pfn_t current_pfn, temp_pfn;
>>>
>>>   	if (info->flag_elf_dumpfile)
>>>   		return FALSE;
>>> @@ -7319,16 +7371,11 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>>>   	threads = info->threads;
>>>   	kdump_thread_args = info->kdump_thread_args;
>>>
>>> -	page_data_num = info->num_buffers;
>>> +	page_buf_num = info->num_buffers;
>>>   	page_data_buf = info->page_data_buf;
>>>
>>> -	for (i = 0; i < page_data_num; i++) {
>>> -		/*
>>> -		 * producer will use pfn in page_data_buf to decide the
>>> -		 * consumed pfn
>>> -		 */
>>> -		page_data_buf[i].pfn = start_pfn - 1;
>>> -		page_data_buf[i].ready = 0;
>>> +	for (i = 0; i < page_buf_num; i++) {
>>> +		page_data_buf[i].used = 0;
>>>   		res = pthread_mutex_init(&page_data_buf[i].mutex, NULL);
>>>   		if (res != 0) {
>>>   			ERRMSG("Can't initialize mutex of page_data_buf. %s\n",
>>> @@ -7342,8 +7389,9 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>>>   		kdump_thread_args[i].len_buf_out = len_buf_out;
>>>   		kdump_thread_args[i].start_pfn = start_pfn;
>>>   		kdump_thread_args[i].end_pfn = end_pfn;
>>> -		kdump_thread_args[i].page_data_num = page_data_num;
>>> +		kdump_thread_args[i].page_buf_num = page_buf_num;
>>>   		kdump_thread_args[i].page_data_buf = page_data_buf;
>>> +		kdump_thread_args[i].page_flag_buf = info->page_flag_buf[i];
>>>   		kdump_thread_args[i].cycle = cycle;
>>>
>>>   		res = pthread_create(threads[i], NULL,
>>> @@ -7356,55 +7404,94 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>>>   		}
>>>   	}
>>>
>>> -	consuming_pfn = start_pfn;
>>> -	index = -1;
>>> +	while (1) {
>>> +		consuming = 0;
>>> +		check_count = 0;
>>> +		end_count = 0;
>>>
>>> -	gettimeofday(&last, NULL);
>>> +		/*
>>> +		 * The basic idea is producer producing page and consumer writing page.
>>> +		 * Each producer have a page_flag_buf list which is used for storing page's description.
>>> +		 * The size of page_flag_buf is little so it won't take too much memory.
>>> +		 * And all producers will share a page_data_buf array which is used for storing page's compressed data.
>>> +		 * The main thread is the consumer. It will find the next pfn and write it into file.
>>> +		 * The next pfn is smallest pfn in all page_flag_buf.
>>> +		 */
>>> +		while (1) {
>>> +			current_pfn = end_pfn;
>>>
>>> -	while (consuming_pfn < end_pfn) {
>>> -		index = consuming_pfn % page_data_num;
>>> +			/*
>>> +			 * page_flag_buf is in circular linked list.
>>> +			 * The array info->page_flag_buf[] records the current page_flag_buf in each thread's
>>> +			 * page_flag_buf list.
>>> +			 * consuming is used for recording in which thread the pfn is the smallest.
>>> +			 * current_pfn is used for recording the value of pfn when checking the pfn.
>>> +			 */
>>> +			for (i = 0; i < info->num_threads; i++) {
>>> +				if (info->page_flag_buf[i]->ready == FLAG_UNUSED)
>>> +					continue;
>>> +				temp_pfn = info->page_flag_buf[i]->pfn;
>>>
>>> -		gettimeofday(&new, NULL);
>>> -		if (new.tv_sec - last.tv_sec > WAIT_TIME) {
>>> -			ERRMSG("Can't get data of pfn %llx.\n", consuming_pfn);
>>> -			goto out;
>>> -		}
>>> +				/*
>>> +				 * count how many threads have reached the end.
>>> +				 */
>>> +				if (temp_pfn >= end_pfn) {
>>> +					end_count++;
>>> +					info->page_flag_buf[i]->ready = FLAG_UNUSED;
>>> +					continue;
>>> +				}
>>>
>>> -		/*
>>> -		 * check pfn first without mutex locked to reduce the time
>>> -		 * trying to lock the mutex
>>> -		 */
>>> -		if (page_data_buf[index].pfn != consuming_pfn)
>>> -			continue;
>>> +				if (current_pfn < temp_pfn)
>>> +					continue;
>>>
>>> -		if (pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
>>> -			continue;
>>> +				check_count++;
>>> +				consuming = i;
>>> +				current_pfn = temp_pfn;
>>> +			}
>>> +
>>> +			/*
>>> +			 * If all the threads have reached the end, we will finish writing.
>>> +			 */
>>> +			if (end_count >= info->num_threads)
>>> +				goto finish;
>>> +
>>> +			/*
>>> +			 * Since it has the probabilty that there is no page_flag_buf being ready,
>>> +			 * we should recheck if it happens.
>>> +			 */
>>> +			if (check_count == 0)
>>> +				continue;
>>> +
>>> +			/*
>>> +			 * When we check the pfn in page_flag_buf, it may be being produced.
>>> +			 * So we should wait until it is ready to use. And if the pfn is
>>> +			 * different from the value when we check, we should rechoose the buf.
>>> +			 */
>>> +			gettimeofday(&last, NULL);
>>> +			while (info->page_flag_buf[consuming]->ready != FLAG_READY) {
>>> +				gettimeofday(&new, NULL);
>>> +				if (new.tv_sec - last.tv_sec > WAIT_TIME) {
>>> +					ERRMSG("Can't get data of pfn.\n");
>>> +					goto out;
>>> +				}
>>> +			}
>>>
>>> -		/* check whether the found one is ready to be consumed */
>>> -		if (page_data_buf[index].pfn != consuming_pfn ||
>>> -		    page_data_buf[index].ready != 1) {
>>> -			goto unlock;
>>> +			if (current_pfn == info->page_flag_buf[consuming]->pfn)
>>> +				break;
>>>   		}
>>>
>>>   		if ((num_dumped % per) == 0)
>>>   			print_progress(PROGRESS_COPY, num_dumped, info->num_dumpable);
>>>
>>> -		/* next pfn is found, refresh last here */
>>> -		last = new;
>>> -		consuming_pfn++;
>>> -		info->consumed_pfn++;
>>> -		page_data_buf[index].ready = 0;
>>> -
>>> -		if (page_data_buf[index].dumpable == FALSE)
>>> -			goto unlock;
>>> -
>>>   		num_dumped++;
>>>
>>> -		if (page_data_buf[index].zero == TRUE) {
>>> +
>>> +		if (info->page_flag_buf[consuming]->zero == TRUE) {
>>>   			if (!write_cache(cd_header, pd_zero, sizeof(page_desc_t)))
>>>   				goto out;
>>>   			pfn_zero++;
>>>   		} else {
>>> +			index = info->page_flag_buf[consuming]->index;
>>>   			pd.flags      = page_data_buf[index].flags;
>>>   			pd.size       = page_data_buf[index].size;
>>>   			pd.page_flags = 0;
>>> @@ -7420,12 +7507,12 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>>>   			 */
>>>   			if (!write_cache(cd_page, page_data_buf[index].buf, pd.size))
>>>   				goto out;
>>> -
>>> +			page_data_buf[index].used = 0;
>>>   		}
>>> -unlock:
>>> -		pthread_mutex_unlock(&page_data_buf[index].mutex);
>>> +		info->page_flag_buf[consuming]->ready = FLAG_UNUSED;
>>> +		info->page_flag_buf[consuming] = info->page_flag_buf[consuming]->next;
>>>   	}
>>> -
>>> +finish:
>>>   	ret = TRUE;
>>>   	/*
>>>   	 * print [100 %]
>>> @@ -7464,7 +7551,7 @@ out:
>>>   	}
>>>
>>>   	if (page_data_buf != NULL) {
>>> -		for (i = 0; i < page_data_num; i++) {
>>> +		for (i = 0; i < page_buf_num; i++) {
>>>   			pthread_mutex_destroy(&page_data_buf[i].mutex);
>>>   		}
>>>   	}
>>> @@ -7564,6 +7651,7 @@ write_kdump_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_pag
>>>   		num_dumped++;
>>>   		if (!read_pfn(pfn, buf))
>>>   			goto out;
>>> +
>>>   		filter_data_buffer(buf, pfn_to_paddr(pfn), info->page_size);
>>>
>>>   		/*
>>> diff --git a/makedumpfile.h b/makedumpfile.h
>>> index e0b5bbf..8a9a5b2 100644
>>> --- a/makedumpfile.h
>>> +++ b/makedumpfile.h
>>> @@ -977,7 +977,7 @@ typedef unsigned long long int ulonglong;
>>>   #define PAGE_DATA_NUM	(50)
>>>   #define WAIT_TIME	(60 * 10)
>>>   #define PTHREAD_FAIL	((void *)-2)
>>> -#define NUM_BUFFERS	(50)
>>> +#define NUM_BUFFERS	(20)
>>>
>>>   struct mmap_cache {
>>>   	char	*mmap_buf;
>>> @@ -985,28 +985,36 @@ struct mmap_cache {
>>>   	off_t   mmap_end_offset;
>>>   };
>>>
>>> +enum {
>>> +	FLAG_UNUSED,
>>> +	FLAG_READY,
>>> +	FLAG_FILLING
>>> +};
>>> +struct page_flag {
>>> +	mdf_pfn_t pfn;
>>> +	char zero;
>>> +	char ready;
>>> +	short index;
>>> +	struct page_flag *next;
>>> +};
>>> +
>>>   struct page_data
>>>   {
>>> -	mdf_pfn_t pfn;
>>> -	int dumpable;
>>> -	int zero;
>>> -	unsigned int flags;
>>> +	pthread_mutex_t mutex;
>>>   	long size;
>>>   	unsigned char *buf;
>>> -	pthread_mutex_t mutex;
>>> -	/*
>>> -	 * whether the page_data is ready to be consumed
>>> -	 */
>>> -	int ready;
>>> +	int flags;
>>> +	int used;
>>>   };
>>>
>>>   struct thread_args {
>>>   	int thread_num;
>>>   	unsigned long len_buf_out;
>>>   	mdf_pfn_t start_pfn, end_pfn;
>>> -	int page_data_num;
>>> +	int page_buf_num;
>>>   	struct cycle *cycle;
>>>   	struct page_data *page_data_buf;
>>> +	struct page_flag *page_flag_buf;
>>>   };
>>>
>>>   /*
>>> @@ -1295,6 +1303,7 @@ struct DumpInfo {
>>>   	pthread_t **threads;
>>>   	struct thread_args *kdump_thread_args;
>>>   	struct page_data *page_data_buf;
>>> +	struct page_flag **page_flag_buf;
>>>   	pthread_rwlock_t usemmap_rwlock;
>>>   	mdf_pfn_t current_pfn;
>>>   	pthread_mutex_t current_pfn_mutex;
>>> --
>>> 1.8.3.1
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> kexec mailing list
>>> kexec@lists.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/kexec
>>
>> _______________________________________________
>> kexec mailing list
>> kexec@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/kexec
>
>



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Re: [PATCH v1] Improve the performance of --num-threads -d 31

["Zhou, Wenjian/周文剑"]

On 02/15/2016 10:15 AM, "Zhou, Wenjian/周文剑" wrote:
> Hello Usui,
>
> Thanks very much for your comments.
> And sorry for the late reply.
>
> See below.
>
> On 02/08/2016 01:00 PM, Minoru Usui wrote:
>> Hello,
>>
>>> -----Original Message-----
>>> From: kexec [mailto:kexec-bounces@lists.infradead.org] On Behalf Of Minoru Usui
>>> Sent: Thursday, February 04, 2016 8:52 AM
>>> To: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>; kexec@lists.infradead.org
>>> Subject: Re: [PATCH v1] Improve the performance of --num-threads -d 31
>>>
>>> Hi, Zhou
>>>
>>> I have some comments.
>>> I'm sorry if I have misunderstood your code.
>>>
>>>> -----Original Message-----
>>>> From: kexec [mailto:kexec-bounces@lists.infradead.org] On Behalf Of Zhou Wenjian
>>>> Sent: Monday, February 01, 2016 3:22 PM
>>>> To: kexec@lists.infradead.org
>>>> Subject: [PATCH v1] Improve the performance of --num-threads -d 31
>>>>
>>>> v1:
>>>>          1. change page_flag.ready's value to enum
>>>>          2. change the patch description
>>>>          3. cleanup some codes
>>>>     4. fix a bug in cyclic mode
>>>>
>>>> multi-threads implementation will introduce extra cost when handling
>>>> each page. The origin implementation will also do the extra work for
>>>> filtered pages. So there is a big performance degradation in
>>>> --num-threads -d 31.
>>>> The new implementation won't do the extra work for filtered pages any
>>>> more. So the performance of -d 31 is close to that of serial processing.
>>>>
>>>> The new implementation is just like the following:
>>>>          * The basic idea is producer producing page and consumer writing page.
>>>>          * Each producer have a page_flag_buf list which is used for storing
>>>>            page's description.
>>>>          * The size of page_flag_buf is little so it won't take too much memory.
>>>>          * And all producers will share a page_data_buf array which is
>>>>            used for storing page's compressed data.
>>>>          * The main thread is the consumer. It will find the next pfn and write
>>>>            it into file.
>>>>          * The next pfn is smallest pfn in all page_flag_buf.
>>>>
>>>> Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>
>>>> ---
>>>>   makedumpfile.c | 258 ++++++++++++++++++++++++++++++++++++++-------------------
>>>>   makedumpfile.h |  31 ++++---
>>>>   2 files changed, 193 insertions(+), 96 deletions(-)
>>>>
>>>> diff --git a/makedumpfile.c b/makedumpfile.c
>>>> index fa0b779..0ecd065 100644
>>>> --- a/makedumpfile.c
>>>> +++ b/makedumpfile.c
>>>> @@ -3483,7 +3483,8 @@ initial_for_parallel()
>>>>       unsigned long page_data_buf_size;
>>>>       unsigned long limit_size;
>>>>       int page_data_num;
>>>> -    int i;
>>>> +    struct page_flag *current;
>>>> +    int i, j;
>>>>
>>>>       len_buf_out = calculate_len_buf_out(info->page_size);
>>>>
>>>> @@ -3562,8 +3563,10 @@ initial_for_parallel()
>>>>                 - MAP_REGION * info->num_threads) * 0.6;
>>>>
>>>>       page_data_num = limit_size / page_data_buf_size;
>>>> +    info->num_buffers = 3 * info->num_threads;
>>>>
>>>> -    info->num_buffers = MIN(NUM_BUFFERS, page_data_num);
>>>> +    info->num_buffers = MAX(info->num_buffers, NUM_BUFFERS);
>>>> +    info->num_buffers = MIN(info->num_buffers, page_data_num);
>>>>
>>>>       DEBUG_MSG("Number of struct page_data for produce/consume: %d\n",
>>>>               info->num_buffers);
>>>> @@ -3588,6 +3591,36 @@ initial_for_parallel()
>>>>       }
>>>>
>>>>       /*
>>>> +     * initial page_flag for each thread
>>>> +     */
>>>> +    if ((info->page_flag_buf = malloc(sizeof(void *) * info->num_threads))
>>>> +        == NULL) {
>>>> +        MSG("Can't allocate memory for page_flag_buf. %s\n",
>>>> +                strerror(errno));
>>>> +        return FALSE;
>>>> +    }
>>>> +    memset(info->page_flag_buf, 0, sizeof(void *) * info->num_threads);
>>>> +
>>>> +    for (i = 0; i < info->num_threads; i++) {
>>>> +        if ((info->page_flag_buf[i] = malloc(sizeof(struct page_flag))) == NULL) {
>>>
>>> Fist element of struct page_flag in circular list is allocated by malloc(),
>>> but other elements are allocated by calloc().(see below)
>>> I think both elements should be allocated by calloc().
>>>
>
> Yes, you are right.
> I have made a mistake.
>
>>>> +            MSG("Can't allocate memory for page_flag_buf. %s\n",
>>>> +                strerror(errno));
>>>> +            return FALSE;
>>>> +        }
>>>> +        current = info->page_flag_buf[i];
>>>> +
>>>> +        for (j = 1; j < NUM_BUFFERS; j++) {
>>>> +            if ((current->next = calloc(0, sizeof(struct page_flag))) == NULL) {
>>>> +                MSG("Can't allocate memory for data of page_data_buf. %s\n",
>>>> +                    strerror(errno));
>>>> +                return FALSE;
>>>> +            }
>>>
>>>
>>> First argument of calloc() should be 1, not 0.
>>> And there is typo in error message.
>>> Allocated element is not page_data_buf.
>>>
>
> I agree.
>
>>>> +            current = current->next;
>>>> +        }
>>>> +        current->next = info->page_flag_buf[i];
>>>> +    }
>>>> +
>>>> +    /*
>>>>        * initial fd_memory for threads
>>>>        */
>>>>       for (i = 0; i < info->num_threads; i++) {
>>>> @@ -3612,7 +3645,8 @@ initial_for_parallel()
>>>>   void
>>>>   free_for_parallel()
>>>>   {
>>>> -    int i;
>>>> +    int i, j;
>>>> +    struct page_flag *current;
>>>>
>>>>       if (info->threads != NULL) {
>>>>           for (i = 0; i < info->num_threads; i++) {
>>>> @@ -3655,6 +3689,19 @@ free_for_parallel()
>>>>           free(info->page_data_buf);
>>>>       }
>>>>
>>>> +    if (info->page_flag_buf != NULL) {
>>>> +        for (i = 0; i < info->num_threads; i++) {
>>>> +            for (j = 0; j < NUM_BUFFERS; j++) {
>>>> +                if (info->page_flag_buf[i] != NULL) {
>>>> +                    current = info->page_flag_buf[i];
>>>> +                    info->page_flag_buf[i] = current->next;
>>>> +                    free(current);
>>>> +                }
>>>> +            }
>>>> +        }
>>>> +        free(info->page_flag_buf);
>>>> +    }
>>>> +
>>>>       if (info->parallel_info == NULL)
>>>>           return;
>>>>
>>>> @@ -7076,10 +7123,10 @@ kdump_thread_function_cyclic(void *arg) {
>>>>       void *retval = PTHREAD_FAIL;
>>>>       struct thread_args *kdump_thread_args = (struct thread_args *)arg;
>>>>       struct page_data *page_data_buf = kdump_thread_args->page_data_buf;
>>>> +    struct page_flag *page_flag_buf = kdump_thread_args->page_flag_buf;
>>>>       struct cycle *cycle = kdump_thread_args->cycle;
>>>> -    int page_data_num = kdump_thread_args->page_data_num;
>>>>       mdf_pfn_t pfn;
>>>> -    int index;
>>>> +    int index = kdump_thread_args->thread_num;
>>>>       int buf_ready;
>>>>       int dumpable;
>>>>       int fd_memory = 0;
>>>> @@ -7125,47 +7172,47 @@ kdump_thread_function_cyclic(void *arg) {
>>>>                           kdump_thread_args->thread_num);
>>>>       }
>>>>
>>>> -    while (1) {
>>>> -        /* get next pfn */
>>>> -        pthread_mutex_lock(&info->current_pfn_mutex);
>>>> -        pfn = info->current_pfn;
>>>> -        info->current_pfn++;
>>>> -        pthread_mutex_unlock(&info->current_pfn_mutex);
>>>> +    /*
>>>> +     * filtered page won't take anything
>>>> +     * unfiltered zero page will only take a page_flag_buf
>>>> +     * unfiltered non-zero page will take a page_flag_buf and a page_data_buf
>>>> +     */
>>>> +    while (page_flag_buf->pfn < kdump_thread_args->end_pfn) {
>>>
>>> At first, page_flag_buf->pfn is not initialized.
>>> I think this block should be replaced with the following code.
>>>
>>> ===
>>>    do {
>>>      :
>>>    } while(page_flag_buf->pfn < kdump_thread_args->end_pfn)
>>> ===
>>
>> I'm sorry, above suggestion is meaningless in terms of page_flag_buf->pfn is uninitialized.
>> It should be replaced like following.
>>
>> ===
>>    while (1) {
>>      :
>>      while (buf_ready == FALSE) {
>>         :
>>        if (pfn >= kdump_thread_args->end_pfn) {
>>           :
>>          goto finish;
>>        }
>>        :
>>      }
>>      :
>>    }
>> finish:
>> ===
>>
>
> page_flag_buf is allocated by calloc().
> The page_flag_buf->pfn's value is 0.
> So I think it is not necessary to modify the code.
>
>> Thanks,
>> Minoru Usui
>>
>>
>>>> +        buf_ready = FALSE;
>>>>
>>>> -        if (pfn >= kdump_thread_args->end_pfn)
>>>> -            break;
>>>> +        while (page_data_buf[index].used != 0 ||
>>>> +                pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
>>>> +            index = (index + 1) % info->num_buffers;
>>>>
>>>> -        index = -1;
>>>> -        buf_ready = FALSE;
>>>> +        page_data_buf[index].used = 1;
>>>
>>> "1" is a magic number.
>>> It should be changed TRUE or FALSE.
>>>
>
> I see.
>
>>>>           while (buf_ready == FALSE) {
>>>>               pthread_testcancel();
>>>> -
>>>> -            index = pfn % page_data_num;
>>>> -
>>>> -            if (pfn - info->consumed_pfn > info->num_buffers)
>>>> +            if (page_flag_buf->ready == FLAG_READY)
>>>>                   continue;
>>>
>>> At first, page_flag_buf->ready is uninitialized, too.
>>> Should it be initialized in head part of this function, even if FLAG_UNUSED is defined 0?
>>>
>>>
>
> The same topic as the page_flag_buf is allocated by calloc().
>
>>>>
>>>> -            if (page_data_buf[index].ready != 0)
>>>> -                continue;
>>>> -
>>>> -            pthread_mutex_lock(&page_data_buf[index].mutex);
>>>> +            /* get next pfn */
>>>> +            pthread_mutex_lock(&info->current_pfn_mutex);
>>>> +            pfn = info->current_pfn;
>>>> +            info->current_pfn++;
>>>> +            page_flag_buf->ready = FLAG_FILLING;
>>>> +            pthread_mutex_unlock(&info->current_pfn_mutex);
>>>>
>>>> -            if (page_data_buf[index].ready != 0)
>>>> -                goto unlock;
>>>> +            page_flag_buf->pfn = pfn;
>>>
>>> It set FLAG_FILLING to page_flag_buf->ready before setting pfn to page_flag_buf->pfn.
>>> But consumer gets page_flag_buf->pfn after checking page_flag_buf->ready != FLAG_UNUSED
>>> in getting minimum pfn of each thread block.
>>> Should it set page_flag_buf->pfn first?
>>>
>
> Have you noticed the following code in the consumer?
> <cut>
>                          if (current_pfn == info->page_flag_buf[consuming]->pfn)
>                                  break;
> <cut>
>
> The consumer will check if the pfn is changed after the page_flag_buf->ready turns to be FLAG_READY.
> So it's not important whether setting page_flag_buf->pfn first or not.
>
> In the other hand, even setting page_flag_buf->pfn first, if the pfn is not dumpable, the producer
> will also reset the page_flag_buf->pfn.
>
>>>>
>>>> -            buf_ready = TRUE;
>>>> -
>>>> -            page_data_buf[index].pfn = pfn;
>>>> -            page_data_buf[index].ready = 1;
>>>> +            if (pfn >= kdump_thread_args->end_pfn) {
>>>> +                page_data_buf[index].used = 0;
>>>> +                page_flag_buf->ready = FLAG_READY;
>>>> +                info->current_pfn--;
>>>> +                break;
>>>> +            }
>>>
>>> This block decrements info->current_pfn without info->current_pfn_mutex.
>>> I think this block should be moved into previous pthread_mutex_lock(info->current_pfn_mutex) block, so it can remove.
>>>
>
> Why do you think it should have current_pfn_mutex?
>
> If pfn >= kdump_thread_args->end_pfn, info->current_pfn will always larger than
> kdump_thread_args->end_pfn. info->current_pfn-- won't affect anything.
>
> The decrement operation is for cyclic mode.
>

Sorry, it seems I was wrong.
It can't work well in cyclic mode.
I will fix it in the next version.

-- 
Thanks
Zhou




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Re: [PATCH v1] Improve the performance of --num-threads -d 31

[Minoru Usui]

Hello Zhou

I'm sorry for late reply, too.

> -----Original Message-----
> From: "Zhou, Wenjian/周文剑" [mailto:zhouwj-fnst@cn.fujitsu.com]
> Sent: Monday, February 15, 2016 11:15 AM
> To: Usui Minoru(碓井 成) <min-usui@ti.jp.nec.com>; kexec@lists.infradead.org
> Subject: Re: [PATCH v1] Improve the performance of --num-threads -d 31
> 
> Hello Usui,
> 
> Thanks very much for your comments.
> And sorry for the late reply.
> 
> See below.
> 
> On 02/08/2016 01:00 PM, Minoru Usui wrote:
> > Hello,
> >
> >> -----Original Message-----
> >> From: kexec [mailto:kexec-bounces@lists.infradead.org] On Behalf Of Minoru Usui
> >> Sent: Thursday, February 04, 2016 8:52 AM
> >> To: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>; kexec@lists.infradead.org
> >> Subject: Re: [PATCH v1] Improve the performance of --num-threads -d 31
> >>
> >> Hi, Zhou
> >>
> >> I have some comments.
> >> I'm sorry if I have misunderstood your code.
> >>
> >>> -----Original Message-----
> >>> From: kexec [mailto:kexec-bounces@lists.infradead.org] On Behalf Of Zhou Wenjian
> >>> Sent: Monday, February 01, 2016 3:22 PM
> >>> To: kexec@lists.infradead.org
> >>> Subject: [PATCH v1] Improve the performance of --num-threads -d 31
> >>>
> >>> v1:
> >>>          1. change page_flag.ready's value to enum
> >>>          2. change the patch description
> >>>          3. cleanup some codes
> >>> 	4. fix a bug in cyclic mode
> >>>
> >>> multi-threads implementation will introduce extra cost when handling
> >>> each page. The origin implementation will also do the extra work for
> >>> filtered pages. So there is a big performance degradation in
> >>> --num-threads -d 31.
> >>> The new implementation won't do the extra work for filtered pages any
> >>> more. So the performance of -d 31 is close to that of serial processing.
> >>>
> >>> The new implementation is just like the following:
> >>>          * The basic idea is producer producing page and consumer writing page.
> >>>          * Each producer have a page_flag_buf list which is used for storing
> >>>            page's description.
> >>>          * The size of page_flag_buf is little so it won't take too much memory.
> >>>          * And all producers will share a page_data_buf array which is
> >>>            used for storing page's compressed data.
> >>>          * The main thread is the consumer. It will find the next pfn and write
> >>>            it into file.
> >>>          * The next pfn is smallest pfn in all page_flag_buf.
> >>>
> >>> Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>
> >>> ---
> >>>   makedumpfile.c | 258 ++++++++++++++++++++++++++++++++++++++-------------------
> >>>   makedumpfile.h |  31 ++++---
> >>>   2 files changed, 193 insertions(+), 96 deletions(-)
> >>>
> >>> diff --git a/makedumpfile.c b/makedumpfile.c
> >>> index fa0b779..0ecd065 100644
> >>> --- a/makedumpfile.c
> >>> +++ b/makedumpfile.c
> >>> @@ -3483,7 +3483,8 @@ initial_for_parallel()
> >>>   	unsigned long page_data_buf_size;
> >>>   	unsigned long limit_size;
> >>>   	int page_data_num;
> >>> -	int i;
> >>> +	struct page_flag *current;
> >>> +	int i, j;
> >>>
> >>>   	len_buf_out = calculate_len_buf_out(info->page_size);
> >>>
> >>> @@ -3562,8 +3563,10 @@ initial_for_parallel()
> >>>   		      - MAP_REGION * info->num_threads) * 0.6;
> >>>
> >>>   	page_data_num = limit_size / page_data_buf_size;
> >>> +	info->num_buffers = 3 * info->num_threads;
> >>>
> >>> -	info->num_buffers = MIN(NUM_BUFFERS, page_data_num);
> >>> +	info->num_buffers = MAX(info->num_buffers, NUM_BUFFERS);
> >>> +	info->num_buffers = MIN(info->num_buffers, page_data_num);
> >>>
> >>>   	DEBUG_MSG("Number of struct page_data for produce/consume: %d\n",
> >>>   			info->num_buffers);
> >>> @@ -3588,6 +3591,36 @@ initial_for_parallel()
> >>>   	}
> >>>
> >>>   	/*
> >>> +	 * initial page_flag for each thread
> >>> +	 */
> >>> +	if ((info->page_flag_buf = malloc(sizeof(void *) * info->num_threads))
> >>> +	    == NULL) {
> >>> +		MSG("Can't allocate memory for page_flag_buf. %s\n",
> >>> +				strerror(errno));
> >>> +		return FALSE;
> >>> +	}
> >>> +	memset(info->page_flag_buf, 0, sizeof(void *) * info->num_threads);
> >>> +
> >>> +	for (i = 0; i < info->num_threads; i++) {
> >>> +		if ((info->page_flag_buf[i] = malloc(sizeof(struct page_flag))) == NULL) {
> >>
> >> Fist element of struct page_flag in circular list is allocated by malloc(),
> >> but other elements are allocated by calloc().(see below)
> >> I think both elements should be allocated by calloc().
> >>
> 
> Yes, you are right.
> I have made a mistake.
> 
> >>> +			MSG("Can't allocate memory for page_flag_buf. %s\n",
> >>> +				strerror(errno));
> >>> +			return FALSE;
> >>> +		}
> >>> +		current = info->page_flag_buf[i];
> >>> +
> >>> +		for (j = 1; j < NUM_BUFFERS; j++) {
> >>> +			if ((current->next = calloc(0, sizeof(struct page_flag))) == NULL) {
> >>> +				MSG("Can't allocate memory for data of page_data_buf. %s\n",
> >>> +					strerror(errno));
> >>> +				return FALSE;
> >>> +			}
> >>
> >>
> >> First argument of calloc() should be 1, not 0.
> >> And there is typo in error message.
> >> Allocated element is not page_data_buf.
> >>
> 
> I agree.
> 
> >>> +			current = current->next;
> >>> +		}
> >>> +		current->next = info->page_flag_buf[i];
> >>> +	}
> >>> +
> >>> +	/*
> >>>   	 * initial fd_memory for threads
> >>>   	 */
> >>>   	for (i = 0; i < info->num_threads; i++) {
> >>> @@ -3612,7 +3645,8 @@ initial_for_parallel()
> >>>   void
> >>>   free_for_parallel()
> >>>   {
> >>> -	int i;
> >>> +	int i, j;
> >>> +	struct page_flag *current;
> >>>
> >>>   	if (info->threads != NULL) {
> >>>   		for (i = 0; i < info->num_threads; i++) {
> >>> @@ -3655,6 +3689,19 @@ free_for_parallel()
> >>>   		free(info->page_data_buf);
> >>>   	}
> >>>
> >>> +	if (info->page_flag_buf != NULL) {
> >>> +		for (i = 0; i < info->num_threads; i++) {
> >>> +			for (j = 0; j < NUM_BUFFERS; j++) {
> >>> +				if (info->page_flag_buf[i] != NULL) {
> >>> +					current = info->page_flag_buf[i];
> >>> +					info->page_flag_buf[i] = current->next;
> >>> +					free(current);
> >>> +				}
> >>> +			}
> >>> +		}
> >>> +		free(info->page_flag_buf);
> >>> +	}
> >>> +
> >>>   	if (info->parallel_info == NULL)
> >>>   		return;
> >>>
> >>> @@ -7076,10 +7123,10 @@ kdump_thread_function_cyclic(void *arg) {
> >>>   	void *retval = PTHREAD_FAIL;
> >>>   	struct thread_args *kdump_thread_args = (struct thread_args *)arg;
> >>>   	struct page_data *page_data_buf = kdump_thread_args->page_data_buf;
> >>> +	struct page_flag *page_flag_buf = kdump_thread_args->page_flag_buf;
> >>>   	struct cycle *cycle = kdump_thread_args->cycle;
> >>> -	int page_data_num = kdump_thread_args->page_data_num;
> >>>   	mdf_pfn_t pfn;
> >>> -	int index;
> >>> +	int index = kdump_thread_args->thread_num;
> >>>   	int buf_ready;
> >>>   	int dumpable;
> >>>   	int fd_memory = 0;
> >>> @@ -7125,47 +7172,47 @@ kdump_thread_function_cyclic(void *arg) {
> >>>   						kdump_thread_args->thread_num);
> >>>   	}
> >>>
> >>> -	while (1) {
> >>> -		/* get next pfn */
> >>> -		pthread_mutex_lock(&info->current_pfn_mutex);
> >>> -		pfn = info->current_pfn;
> >>> -		info->current_pfn++;
> >>> -		pthread_mutex_unlock(&info->current_pfn_mutex);
> >>> +	/*
> >>> +	 * filtered page won't take anything
> >>> +	 * unfiltered zero page will only take a page_flag_buf
> >>> +	 * unfiltered non-zero page will take a page_flag_buf and a page_data_buf
> >>> +	 */
> >>> +	while (page_flag_buf->pfn < kdump_thread_args->end_pfn) {
> >>
> >> At first, page_flag_buf->pfn is not initialized.
> >> I think this block should be replaced with the following code.
> >>
> >> ===
> >>    do {
> >>      :
> >>    } while(page_flag_buf->pfn < kdump_thread_args->end_pfn)
> >> ===
> >
> > I'm sorry, above suggestion is meaningless in terms of page_flag_buf->pfn is uninitialized.
> > It should be replaced like following.
> >
> > ===
> >    while (1) {
> >      :
> >      while (buf_ready == FALSE) {
> >         :
> >        if (pfn >= kdump_thread_args->end_pfn) {
> >           :
> >          goto finish;
> >        }
> >        :
> >      }
> >      :
> >    }
> > finish:
> > ===
> >
> 
> page_flag_buf is allocated by calloc().
> The page_flag_buf->pfn's value is 0.
> So I think it is not necessary to modify the code.
> 
> > Thanks,
> > Minoru Usui
> >
> >
> >>> +		buf_ready = FALSE;
> >>>
> >>> -		if (pfn >= kdump_thread_args->end_pfn)
> >>> -			break;
> >>> +		while (page_data_buf[index].used != 0 ||
> >>> +				pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
> >>> +			index = (index + 1) % info->num_buffers;
> >>>
> >>> -		index = -1;
> >>> -		buf_ready = FALSE;
> >>> +		page_data_buf[index].used = 1;
> >>
> >> "1" is a magic number.
> >> It should be changed TRUE or FALSE.
> >>
> 
> I see.
> 
> >>>   		while (buf_ready == FALSE) {
> >>>   			pthread_testcancel();
> >>> -
> >>> -			index = pfn % page_data_num;
> >>> -
> >>> -			if (pfn - info->consumed_pfn > info->num_buffers)
> >>> +			if (page_flag_buf->ready == FLAG_READY)
> >>>   				continue;
> >>
> >> At first, page_flag_buf->ready is uninitialized, too.
> >> Should it be initialized in head part of this function, even if FLAG_UNUSED is defined 0?
> >>
> >>
> 
> The same topic as the page_flag_buf is allocated by calloc().
> 
> >>>
> >>> -			if (page_data_buf[index].ready != 0)
> >>> -				continue;
> >>> -
> >>> -			pthread_mutex_lock(&page_data_buf[index].mutex);
> >>> +			/* get next pfn */
> >>> +			pthread_mutex_lock(&info->current_pfn_mutex);
> >>> +			pfn = info->current_pfn;
> >>> +			info->current_pfn++;
> >>> +			page_flag_buf->ready = FLAG_FILLING;
> >>> +			pthread_mutex_unlock(&info->current_pfn_mutex);
> >>>
> >>> -			if (page_data_buf[index].ready != 0)
> >>> -				goto unlock;
> >>> +			page_flag_buf->pfn = pfn;
> >>
> >> It set FLAG_FILLING to page_flag_buf->ready before setting pfn to page_flag_buf->pfn.
> >> But consumer gets page_flag_buf->pfn after checking page_flag_buf->ready != FLAG_UNUSED
> >> in getting minimum pfn of each thread block.
> >> Should it set page_flag_buf->pfn first?
> >>
> 
> Have you noticed the following code in the consumer?
> <cut>
>                          if (current_pfn == info->page_flag_buf[consuming]->pfn)
>                                  break;
> <cut>

No, I pointed following code.
This part accesses info->page_flag_buf[i]->ready, then it accesses info->page_flag_buf[i]->pfn immediately.
So, temp_pfn may be wrong pfn at this moment.

---
                        for (i = 0; i < info->num_threads; i++) {
                                if (info->page_flag_buf[i]->ready == FLAG_UNUSED)
                                        continue;
                                temp_pfn = info->page_flag_buf[i]->pfn;
---

> The consumer will check if the pfn is changed after the page_flag_buf->ready turns to be FLAG_READY.
> So it's not important whether setting page_flag_buf->pfn first or not.

As you said, consumer checks pfn which is changed.
So it works well.

> In the other hand, even setting page_flag_buf->pfn first, if the pfn is not dumpable, the producer
> will also reset the page_flag_buf->pfn.

Thank you for your explanation.
I didn't notice that pfn can be undumpable.

> >>>
> >>> -			buf_ready = TRUE;
> >>> -
> >>> -			page_data_buf[index].pfn = pfn;
> >>> -			page_data_buf[index].ready = 1;
> >>> +			if (pfn >= kdump_thread_args->end_pfn) {
> >>> +				page_data_buf[index].used = 0;
> >>> +				page_flag_buf->ready = FLAG_READY;
> >>> +				info->current_pfn--;
> >>> +				break;
> >>> +			}
> >>
> >> This block decrements info->current_pfn without info->current_pfn_mutex.
> >> I think this block should be moved into previous pthread_mutex_lock(info->current_pfn_mutex) block, so it can remove.
> >>
> 
> Why do you think it should have current_pfn_mutex?
> 
> If pfn >= kdump_thread_args->end_pfn, info->current_pfn will always larger than
> kdump_thread_args->end_pfn. info->current_pfn-- won't affect anything.
> 
> The decrement operation is for cyclic mode.
> 
> >>>
> >>>   			dumpable = is_dumpable(
> >>>   				info->fd_bitmap ? &bitmap_parallel : info->bitmap2,
> >>>   				pfn,
> >>>   				cycle);
> >>> -			page_data_buf[index].dumpable = dumpable;
> >>>   			if (!dumpable)
> >>> -				goto unlock;
> >>> +				continue;
> >>>
> >>>   			if (!read_pfn_parallel(fd_memory, pfn, buf,
> >>>   					       &bitmap_memory_parallel,
> >>> @@ -7178,11 +7225,11 @@ kdump_thread_function_cyclic(void *arg) {
> >>>
> >>>   			if ((info->dump_level & DL_EXCLUDE_ZERO)
> >>>   			    && is_zero_page(buf, info->page_size)) {
> >>> -				page_data_buf[index].zero = TRUE;
> >>> -				goto unlock;
> >>> +				page_flag_buf->zero = TRUE;
> >>> +				goto next;
> >>>   			}
> >>
> >> First, this code gets page_data_buf, then it gets page_flag_buf.
> >> However, if processed pfn is zero page,
> >> it processes next pfn while keeping page_data_buf.
> >>
> >> I think it should get page_flag_buf, then get page_data_buf
> >> in order to shorten the holding period of the page_data_buf[index].mutex.
> >>
> 
> Do you mean the following logic?
> 1. get the page_flag_buf first
> 2. if the pfn is not zero page, then get the page_data_buf.

Yes.

> Think about the following case.
> A producer get the page_flag_buf, and the pfn is not zero page.
> It wants to get a page_data_buf, but there is no more page_data_buf.
> Then ...

It's not a problem.
In not zero page case, this logic needs both page_flag_buf and page_data_buf,
so waiting buffer is obvious when it isn't able to get page_flag_buf or page_data_buf.
 
> Since there are several page_data_bufs, it's not a problem that each producer
> will always hold a page_data_buf.

It depends on the speed of consumer and producer.
It's not possible to predict it.

In zero page case, I think each producer executes more parallel theoretically
if page_data_buf doesn't get.

Thanks,
Minoru Usui

> 
> Thanks again for your comments.
> And I will post the next version later.
> 
> --
> Thanks
> Zhou
> 
> >> Thanks,
> >> Minoru Usui
> >>
> >>>
> >>> -			page_data_buf[index].zero = FALSE;
> >>> +			page_flag_buf->zero = FALSE;
> >>>
> >>>   			/*
> >>>   			 * Compress the page data.
> >>> @@ -7232,12 +7279,16 @@ kdump_thread_function_cyclic(void *arg) {
> >>>   				page_data_buf[index].size  = info->page_size;
> >>>   				memcpy(page_data_buf[index].buf, buf, info->page_size);
> >>>   			}
> >>> -unlock:
> >>> -			pthread_mutex_unlock(&page_data_buf[index].mutex);
> >>> +			page_flag_buf->index = index;
> >>> +			buf_ready = TRUE;
> >>> +next:
> >>> +			page_flag_buf->ready = FLAG_READY;
> >>> +			page_flag_buf = page_flag_buf->next;
> >>>
> >>>   		}
> >>> -	}
> >>>
> >>> +		pthread_mutex_unlock(&page_data_buf[index].mutex);
> >>> +	}
> >>>   	retval = NULL;
> >>>
> >>>   fail:
> >>> @@ -7265,14 +7316,15 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >>>   	struct page_desc pd;
> >>>   	struct timeval tv_start;
> >>>   	struct timeval last, new;
> >>> -	unsigned long long consuming_pfn;
> >>>   	pthread_t **threads = NULL;
> >>>   	struct thread_args *kdump_thread_args = NULL;
> >>>   	void *thread_result;
> >>> -	int page_data_num;
> >>> +	int page_buf_num;
> >>>   	struct page_data *page_data_buf = NULL;
> >>>   	int i;
> >>>   	int index;
> >>> +	int end_count, consuming, check_count;
> >>> +	mdf_pfn_t current_pfn, temp_pfn;
> >>>
> >>>   	if (info->flag_elf_dumpfile)
> >>>   		return FALSE;
> >>> @@ -7319,16 +7371,11 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >>>   	threads = info->threads;
> >>>   	kdump_thread_args = info->kdump_thread_args;
> >>>
> >>> -	page_data_num = info->num_buffers;
> >>> +	page_buf_num = info->num_buffers;
> >>>   	page_data_buf = info->page_data_buf;
> >>>
> >>> -	for (i = 0; i < page_data_num; i++) {
> >>> -		/*
> >>> -		 * producer will use pfn in page_data_buf to decide the
> >>> -		 * consumed pfn
> >>> -		 */
> >>> -		page_data_buf[i].pfn = start_pfn - 1;
> >>> -		page_data_buf[i].ready = 0;
> >>> +	for (i = 0; i < page_buf_num; i++) {
> >>> +		page_data_buf[i].used = 0;
> >>>   		res = pthread_mutex_init(&page_data_buf[i].mutex, NULL);
> >>>   		if (res != 0) {
> >>>   			ERRMSG("Can't initialize mutex of page_data_buf. %s\n",
> >>> @@ -7342,8 +7389,9 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >>>   		kdump_thread_args[i].len_buf_out = len_buf_out;
> >>>   		kdump_thread_args[i].start_pfn = start_pfn;
> >>>   		kdump_thread_args[i].end_pfn = end_pfn;
> >>> -		kdump_thread_args[i].page_data_num = page_data_num;
> >>> +		kdump_thread_args[i].page_buf_num = page_buf_num;
> >>>   		kdump_thread_args[i].page_data_buf = page_data_buf;
> >>> +		kdump_thread_args[i].page_flag_buf = info->page_flag_buf[i];
> >>>   		kdump_thread_args[i].cycle = cycle;
> >>>
> >>>   		res = pthread_create(threads[i], NULL,
> >>> @@ -7356,55 +7404,94 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >>>   		}
> >>>   	}
> >>>
> >>> -	consuming_pfn = start_pfn;
> >>> -	index = -1;
> >>> +	while (1) {
> >>> +		consuming = 0;
> >>> +		check_count = 0;
> >>> +		end_count = 0;
> >>>
> >>> -	gettimeofday(&last, NULL);
> >>> +		/*
> >>> +		 * The basic idea is producer producing page and consumer writing page.
> >>> +		 * Each producer have a page_flag_buf list which is used for storing page's description.
> >>> +		 * The size of page_flag_buf is little so it won't take too much memory.
> >>> +		 * And all producers will share a page_data_buf array which is used for storing page's compressed data.
> >>> +		 * The main thread is the consumer. It will find the next pfn and write it into file.
> >>> +		 * The next pfn is smallest pfn in all page_flag_buf.
> >>> +		 */
> >>> +		while (1) {
> >>> +			current_pfn = end_pfn;
> >>>
> >>> -	while (consuming_pfn < end_pfn) {
> >>> -		index = consuming_pfn % page_data_num;
> >>> +			/*
> >>> +			 * page_flag_buf is in circular linked list.
> >>> +			 * The array info->page_flag_buf[] records the current page_flag_buf in each thread's
> >>> +			 * page_flag_buf list.
> >>> +			 * consuming is used for recording in which thread the pfn is the smallest.
> >>> +			 * current_pfn is used for recording the value of pfn when checking the pfn.
> >>> +			 */
> >>> +			for (i = 0; i < info->num_threads; i++) {
> >>> +				if (info->page_flag_buf[i]->ready == FLAG_UNUSED)
> >>> +					continue;
> >>> +				temp_pfn = info->page_flag_buf[i]->pfn;
> >>>
> >>> -		gettimeofday(&new, NULL);
> >>> -		if (new.tv_sec - last.tv_sec > WAIT_TIME) {
> >>> -			ERRMSG("Can't get data of pfn %llx.\n", consuming_pfn);
> >>> -			goto out;
> >>> -		}
> >>> +				/*
> >>> +				 * count how many threads have reached the end.
> >>> +				 */
> >>> +				if (temp_pfn >= end_pfn) {
> >>> +					end_count++;
> >>> +					info->page_flag_buf[i]->ready = FLAG_UNUSED;
> >>> +					continue;
> >>> +				}
> >>>
> >>> -		/*
> >>> -		 * check pfn first without mutex locked to reduce the time
> >>> -		 * trying to lock the mutex
> >>> -		 */
> >>> -		if (page_data_buf[index].pfn != consuming_pfn)
> >>> -			continue;
> >>> +				if (current_pfn < temp_pfn)
> >>> +					continue;
> >>>
> >>> -		if (pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
> >>> -			continue;
> >>> +				check_count++;
> >>> +				consuming = i;
> >>> +				current_pfn = temp_pfn;
> >>> +			}
> >>> +
> >>> +			/*
> >>> +			 * If all the threads have reached the end, we will finish writing.
> >>> +			 */
> >>> +			if (end_count >= info->num_threads)
> >>> +				goto finish;
> >>> +
> >>> +			/*
> >>> +			 * Since it has the probabilty that there is no page_flag_buf being ready,
> >>> +			 * we should recheck if it happens.
> >>> +			 */
> >>> +			if (check_count == 0)
> >>> +				continue;
> >>> +
> >>> +			/*
> >>> +			 * When we check the pfn in page_flag_buf, it may be being produced.
> >>> +			 * So we should wait until it is ready to use. And if the pfn is
> >>> +			 * different from the value when we check, we should rechoose the buf.
> >>> +			 */
> >>> +			gettimeofday(&last, NULL);
> >>> +			while (info->page_flag_buf[consuming]->ready != FLAG_READY) {
> >>> +				gettimeofday(&new, NULL);
> >>> +				if (new.tv_sec - last.tv_sec > WAIT_TIME) {
> >>> +					ERRMSG("Can't get data of pfn.\n");
> >>> +					goto out;
> >>> +				}
> >>> +			}
> >>>
> >>> -		/* check whether the found one is ready to be consumed */
> >>> -		if (page_data_buf[index].pfn != consuming_pfn ||
> >>> -		    page_data_buf[index].ready != 1) {
> >>> -			goto unlock;
> >>> +			if (current_pfn == info->page_flag_buf[consuming]->pfn)
> >>> +				break;
> >>>   		}
> >>>
> >>>   		if ((num_dumped % per) == 0)
> >>>   			print_progress(PROGRESS_COPY, num_dumped, info->num_dumpable);
> >>>
> >>> -		/* next pfn is found, refresh last here */
> >>> -		last = new;
> >>> -		consuming_pfn++;
> >>> -		info->consumed_pfn++;
> >>> -		page_data_buf[index].ready = 0;
> >>> -
> >>> -		if (page_data_buf[index].dumpable == FALSE)
> >>> -			goto unlock;
> >>> -
> >>>   		num_dumped++;
> >>>
> >>> -		if (page_data_buf[index].zero == TRUE) {
> >>> +
> >>> +		if (info->page_flag_buf[consuming]->zero == TRUE) {
> >>>   			if (!write_cache(cd_header, pd_zero, sizeof(page_desc_t)))
> >>>   				goto out;
> >>>   			pfn_zero++;
> >>>   		} else {
> >>> +			index = info->page_flag_buf[consuming]->index;
> >>>   			pd.flags      = page_data_buf[index].flags;
> >>>   			pd.size       = page_data_buf[index].size;
> >>>   			pd.page_flags = 0;
> >>> @@ -7420,12 +7507,12 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >>>   			 */
> >>>   			if (!write_cache(cd_page, page_data_buf[index].buf, pd.size))
> >>>   				goto out;
> >>> -
> >>> +			page_data_buf[index].used = 0;
> >>>   		}
> >>> -unlock:
> >>> -		pthread_mutex_unlock(&page_data_buf[index].mutex);
> >>> +		info->page_flag_buf[consuming]->ready = FLAG_UNUSED;
> >>> +		info->page_flag_buf[consuming] = info->page_flag_buf[consuming]->next;
> >>>   	}
> >>> -
> >>> +finish:
> >>>   	ret = TRUE;
> >>>   	/*
> >>>   	 * print [100 %]
> >>> @@ -7464,7 +7551,7 @@ out:
> >>>   	}
> >>>
> >>>   	if (page_data_buf != NULL) {
> >>> -		for (i = 0; i < page_data_num; i++) {
> >>> +		for (i = 0; i < page_buf_num; i++) {
> >>>   			pthread_mutex_destroy(&page_data_buf[i].mutex);
> >>>   		}
> >>>   	}
> >>> @@ -7564,6 +7651,7 @@ write_kdump_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_pag
> >>>   		num_dumped++;
> >>>   		if (!read_pfn(pfn, buf))
> >>>   			goto out;
> >>> +
> >>>   		filter_data_buffer(buf, pfn_to_paddr(pfn), info->page_size);
> >>>
> >>>   		/*
> >>> diff --git a/makedumpfile.h b/makedumpfile.h
> >>> index e0b5bbf..8a9a5b2 100644
> >>> --- a/makedumpfile.h
> >>> +++ b/makedumpfile.h
> >>> @@ -977,7 +977,7 @@ typedef unsigned long long int ulonglong;
> >>>   #define PAGE_DATA_NUM	(50)
> >>>   #define WAIT_TIME	(60 * 10)
> >>>   #define PTHREAD_FAIL	((void *)-2)
> >>> -#define NUM_BUFFERS	(50)
> >>> +#define NUM_BUFFERS	(20)
> >>>
> >>>   struct mmap_cache {
> >>>   	char	*mmap_buf;
> >>> @@ -985,28 +985,36 @@ struct mmap_cache {
> >>>   	off_t   mmap_end_offset;
> >>>   };
> >>>
> >>> +enum {
> >>> +	FLAG_UNUSED,
> >>> +	FLAG_READY,
> >>> +	FLAG_FILLING
> >>> +};
> >>> +struct page_flag {
> >>> +	mdf_pfn_t pfn;
> >>> +	char zero;
> >>> +	char ready;
> >>> +	short index;
> >>> +	struct page_flag *next;
> >>> +};
> >>> +
> >>>   struct page_data
> >>>   {
> >>> -	mdf_pfn_t pfn;
> >>> -	int dumpable;
> >>> -	int zero;
> >>> -	unsigned int flags;
> >>> +	pthread_mutex_t mutex;
> >>>   	long size;
> >>>   	unsigned char *buf;
> >>> -	pthread_mutex_t mutex;
> >>> -	/*
> >>> -	 * whether the page_data is ready to be consumed
> >>> -	 */
> >>> -	int ready;
> >>> +	int flags;
> >>> +	int used;
> >>>   };
> >>>
> >>>   struct thread_args {
> >>>   	int thread_num;
> >>>   	unsigned long len_buf_out;
> >>>   	mdf_pfn_t start_pfn, end_pfn;
> >>> -	int page_data_num;
> >>> +	int page_buf_num;
> >>>   	struct cycle *cycle;
> >>>   	struct page_data *page_data_buf;
> >>> +	struct page_flag *page_flag_buf;
> >>>   };
> >>>
> >>>   /*
> >>> @@ -1295,6 +1303,7 @@ struct DumpInfo {
> >>>   	pthread_t **threads;
> >>>   	struct thread_args *kdump_thread_args;
> >>>   	struct page_data *page_data_buf;
> >>> +	struct page_flag **page_flag_buf;
> >>>   	pthread_rwlock_t usemmap_rwlock;
> >>>   	mdf_pfn_t current_pfn;
> >>>   	pthread_mutex_t current_pfn_mutex;
> >>> --
> >>> 1.8.3.1
> >>>
> >>>
> >>>
> >>>
> >>> _______________________________________________
> >>> kexec mailing list
> >>> kexec@lists.infradead.org
> >>> http://lists.infradead.org/mailman/listinfo/kexec
> >>
> >> _______________________________________________
> >> kexec mailing list
> >> kexec@lists.infradead.org
> >> http://lists.infradead.org/mailman/listinfo/kexec
> >
> >
> 

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Re: [PATCH v1] Improve the performance of --num-threads -d 31

["Zhou, Wenjian/周文剑"]

On 02/23/2016 10:16 AM, Minoru Usui wrote:
> Hello Zhou
>
> I'm sorry for late reply, too.
>
>> -----Original Message-----
>> From: "Zhou, Wenjian/周文剑" [mailto:zhouwj-fnst@cn.fujitsu.com]
>> Sent: Monday, February 15, 2016 11:15 AM
>> To: Usui Minoru(碓井 成) <min-usui@ti.jp.nec.com>; kexec@lists.infradead.org
>> Subject: Re: [PATCH v1] Improve the performance of --num-threads -d 31
>>
>> Hello Usui,
>>
>> Thanks very much for your comments.
>> And sorry for the late reply.
>>
>> See below.
>>
>> On 02/08/2016 01:00 PM, Minoru Usui wrote:
>>> Hello,
>>>
>>>> -----Original Message-----
>>>> From: kexec [mailto:kexec-bounces@lists.infradead.org] On Behalf Of Minoru Usui
>>>> Sent: Thursday, February 04, 2016 8:52 AM
>>>> To: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>; kexec@lists.infradead.org
>>>> Subject: Re: [PATCH v1] Improve the performance of --num-threads -d 31
>>>>
>>>> Hi, Zhou
>>>>
>>>> I have some comments.
>>>> I'm sorry if I have misunderstood your code.
>>>>
>>>>> -----Original Message-----
>>>>> From: kexec [mailto:kexec-bounces@lists.infradead.org] On Behalf Of Zhou Wenjian
>>>>> Sent: Monday, February 01, 2016 3:22 PM
>>>>> To: kexec@lists.infradead.org
>>>>> Subject: [PATCH v1] Improve the performance of --num-threads -d 31
>>>>>
>>>>> v1:
>>>>>           1. change page_flag.ready's value to enum
>>>>>           2. change the patch description
>>>>>           3. cleanup some codes
>>>>> 	4. fix a bug in cyclic mode
>>>>>
>>>>> multi-threads implementation will introduce extra cost when handling
>>>>> each page. The origin implementation will also do the extra work for
>>>>> filtered pages. So there is a big performance degradation in
>>>>> --num-threads -d 31.
>>>>> The new implementation won't do the extra work for filtered pages any
>>>>> more. So the performance of -d 31 is close to that of serial processing.
>>>>>
>>>>> The new implementation is just like the following:
>>>>>           * The basic idea is producer producing page and consumer writing page.
>>>>>           * Each producer have a page_flag_buf list which is used for storing
>>>>>             page's description.
>>>>>           * The size of page_flag_buf is little so it won't take too much memory.
>>>>>           * And all producers will share a page_data_buf array which is
>>>>>             used for storing page's compressed data.
>>>>>           * The main thread is the consumer. It will find the next pfn and write
>>>>>             it into file.
>>>>>           * The next pfn is smallest pfn in all page_flag_buf.
>>>>>
>>>>> Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>
>>>>> ---
>>>>>    makedumpfile.c | 258 ++++++++++++++++++++++++++++++++++++++-------------------
>>>>>    makedumpfile.h |  31 ++++---
>>>>>    2 files changed, 193 insertions(+), 96 deletions(-)
>>>>>
>>>>> diff --git a/makedumpfile.c b/makedumpfile.c
>>>>> index fa0b779..0ecd065 100644
>>>>> --- a/makedumpfile.c
>>>>> +++ b/makedumpfile.c
>>>>> @@ -3483,7 +3483,8 @@ initial_for_parallel()
>>>>>    	unsigned long page_data_buf_size;
>>>>>    	unsigned long limit_size;
>>>>>    	int page_data_num;
>>>>> -	int i;
>>>>> +	struct page_flag *current;
>>>>> +	int i, j;
>>>>>
>>>>>    	len_buf_out = calculate_len_buf_out(info->page_size);
>>>>>
>>>>> @@ -3562,8 +3563,10 @@ initial_for_parallel()
>>>>>    		      - MAP_REGION * info->num_threads) * 0.6;
>>>>>
>>>>>    	page_data_num = limit_size / page_data_buf_size;
>>>>> +	info->num_buffers = 3 * info->num_threads;
>>>>>
>>>>> -	info->num_buffers = MIN(NUM_BUFFERS, page_data_num);
>>>>> +	info->num_buffers = MAX(info->num_buffers, NUM_BUFFERS);
>>>>> +	info->num_buffers = MIN(info->num_buffers, page_data_num);
>>>>>
>>>>>    	DEBUG_MSG("Number of struct page_data for produce/consume: %d\n",
>>>>>    			info->num_buffers);
>>>>> @@ -3588,6 +3591,36 @@ initial_for_parallel()
>>>>>    	}
>>>>>
>>>>>    	/*
>>>>> +	 * initial page_flag for each thread
>>>>> +	 */
>>>>> +	if ((info->page_flag_buf = malloc(sizeof(void *) * info->num_threads))
>>>>> +	    == NULL) {
>>>>> +		MSG("Can't allocate memory for page_flag_buf. %s\n",
>>>>> +				strerror(errno));
>>>>> +		return FALSE;
>>>>> +	}
>>>>> +	memset(info->page_flag_buf, 0, sizeof(void *) * info->num_threads);
>>>>> +
>>>>> +	for (i = 0; i < info->num_threads; i++) {
>>>>> +		if ((info->page_flag_buf[i] = malloc(sizeof(struct page_flag))) == NULL) {
>>>>
>>>> Fist element of struct page_flag in circular list is allocated by malloc(),
>>>> but other elements are allocated by calloc().(see below)
>>>> I think both elements should be allocated by calloc().
>>>>
>>
>> Yes, you are right.
>> I have made a mistake.
>>
>>>>> +			MSG("Can't allocate memory for page_flag_buf. %s\n",
>>>>> +				strerror(errno));
>>>>> +			return FALSE;
>>>>> +		}
>>>>> +		current = info->page_flag_buf[i];
>>>>> +
>>>>> +		for (j = 1; j < NUM_BUFFERS; j++) {
>>>>> +			if ((current->next = calloc(0, sizeof(struct page_flag))) == NULL) {
>>>>> +				MSG("Can't allocate memory for data of page_data_buf. %s\n",
>>>>> +					strerror(errno));
>>>>> +				return FALSE;
>>>>> +			}
>>>>
>>>>
>>>> First argument of calloc() should be 1, not 0.
>>>> And there is typo in error message.
>>>> Allocated element is not page_data_buf.
>>>>
>>
>> I agree.
>>
>>>>> +			current = current->next;
>>>>> +		}
>>>>> +		current->next = info->page_flag_buf[i];
>>>>> +	}
>>>>> +
>>>>> +	/*
>>>>>    	 * initial fd_memory for threads
>>>>>    	 */
>>>>>    	for (i = 0; i < info->num_threads; i++) {
>>>>> @@ -3612,7 +3645,8 @@ initial_for_parallel()
>>>>>    void
>>>>>    free_for_parallel()
>>>>>    {
>>>>> -	int i;
>>>>> +	int i, j;
>>>>> +	struct page_flag *current;
>>>>>
>>>>>    	if (info->threads != NULL) {
>>>>>    		for (i = 0; i < info->num_threads; i++) {
>>>>> @@ -3655,6 +3689,19 @@ free_for_parallel()
>>>>>    		free(info->page_data_buf);
>>>>>    	}
>>>>>
>>>>> +	if (info->page_flag_buf != NULL) {
>>>>> +		for (i = 0; i < info->num_threads; i++) {
>>>>> +			for (j = 0; j < NUM_BUFFERS; j++) {
>>>>> +				if (info->page_flag_buf[i] != NULL) {
>>>>> +					current = info->page_flag_buf[i];
>>>>> +					info->page_flag_buf[i] = current->next;
>>>>> +					free(current);
>>>>> +				}
>>>>> +			}
>>>>> +		}
>>>>> +		free(info->page_flag_buf);
>>>>> +	}
>>>>> +
>>>>>    	if (info->parallel_info == NULL)
>>>>>    		return;
>>>>>
>>>>> @@ -7076,10 +7123,10 @@ kdump_thread_function_cyclic(void *arg) {
>>>>>    	void *retval = PTHREAD_FAIL;
>>>>>    	struct thread_args *kdump_thread_args = (struct thread_args *)arg;
>>>>>    	struct page_data *page_data_buf = kdump_thread_args->page_data_buf;
>>>>> +	struct page_flag *page_flag_buf = kdump_thread_args->page_flag_buf;
>>>>>    	struct cycle *cycle = kdump_thread_args->cycle;
>>>>> -	int page_data_num = kdump_thread_args->page_data_num;
>>>>>    	mdf_pfn_t pfn;
>>>>> -	int index;
>>>>> +	int index = kdump_thread_args->thread_num;
>>>>>    	int buf_ready;
>>>>>    	int dumpable;
>>>>>    	int fd_memory = 0;
>>>>> @@ -7125,47 +7172,47 @@ kdump_thread_function_cyclic(void *arg) {
>>>>>    						kdump_thread_args->thread_num);
>>>>>    	}
>>>>>
>>>>> -	while (1) {
>>>>> -		/* get next pfn */
>>>>> -		pthread_mutex_lock(&info->current_pfn_mutex);
>>>>> -		pfn = info->current_pfn;
>>>>> -		info->current_pfn++;
>>>>> -		pthread_mutex_unlock(&info->current_pfn_mutex);
>>>>> +	/*
>>>>> +	 * filtered page won't take anything
>>>>> +	 * unfiltered zero page will only take a page_flag_buf
>>>>> +	 * unfiltered non-zero page will take a page_flag_buf and a page_data_buf
>>>>> +	 */
>>>>> +	while (page_flag_buf->pfn < kdump_thread_args->end_pfn) {
>>>>
>>>> At first, page_flag_buf->pfn is not initialized.
>>>> I think this block should be replaced with the following code.
>>>>
>>>> ===
>>>>     do {
>>>>       :
>>>>     } while(page_flag_buf->pfn < kdump_thread_args->end_pfn)
>>>> ===
>>>
>>> I'm sorry, above suggestion is meaningless in terms of page_flag_buf->pfn is uninitialized.
>>> It should be replaced like following.
>>>
>>> ===
>>>     while (1) {
>>>       :
>>>       while (buf_ready == FALSE) {
>>>          :
>>>         if (pfn >= kdump_thread_args->end_pfn) {
>>>            :
>>>           goto finish;
>>>         }
>>>         :
>>>       }
>>>       :
>>>     }
>>> finish:
>>> ===
>>>
>>
>> page_flag_buf is allocated by calloc().
>> The page_flag_buf->pfn's value is 0.
>> So I think it is not necessary to modify the code.
>>
>>> Thanks,
>>> Minoru Usui
>>>
>>>
>>>>> +		buf_ready = FALSE;
>>>>>
>>>>> -		if (pfn >= kdump_thread_args->end_pfn)
>>>>> -			break;
>>>>> +		while (page_data_buf[index].used != 0 ||
>>>>> +				pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
>>>>> +			index = (index + 1) % info->num_buffers;
>>>>>
>>>>> -		index = -1;
>>>>> -		buf_ready = FALSE;
>>>>> +		page_data_buf[index].used = 1;
>>>>
>>>> "1" is a magic number.
>>>> It should be changed TRUE or FALSE.
>>>>
>>
>> I see.
>>
>>>>>    		while (buf_ready == FALSE) {
>>>>>    			pthread_testcancel();
>>>>> -
>>>>> -			index = pfn % page_data_num;
>>>>> -
>>>>> -			if (pfn - info->consumed_pfn > info->num_buffers)
>>>>> +			if (page_flag_buf->ready == FLAG_READY)
>>>>>    				continue;
>>>>
>>>> At first, page_flag_buf->ready is uninitialized, too.
>>>> Should it be initialized in head part of this function, even if FLAG_UNUSED is defined 0?
>>>>
>>>>
>>
>> The same topic as the page_flag_buf is allocated by calloc().
>>
>>>>>
>>>>> -			if (page_data_buf[index].ready != 0)
>>>>> -				continue;
>>>>> -
>>>>> -			pthread_mutex_lock(&page_data_buf[index].mutex);
>>>>> +			/* get next pfn */
>>>>> +			pthread_mutex_lock(&info->current_pfn_mutex);
>>>>> +			pfn = info->current_pfn;
>>>>> +			info->current_pfn++;
>>>>> +			page_flag_buf->ready = FLAG_FILLING;
>>>>> +			pthread_mutex_unlock(&info->current_pfn_mutex);
>>>>>
>>>>> -			if (page_data_buf[index].ready != 0)
>>>>> -				goto unlock;
>>>>> +			page_flag_buf->pfn = pfn;
>>>>
>>>> It set FLAG_FILLING to page_flag_buf->ready before setting pfn to page_flag_buf->pfn.
>>>> But consumer gets page_flag_buf->pfn after checking page_flag_buf->ready != FLAG_UNUSED
>>>> in getting minimum pfn of each thread block.
>>>> Should it set page_flag_buf->pfn first?
>>>>
>>
>> Have you noticed the following code in the consumer?
>> <cut>
>>                           if (current_pfn == info->page_flag_buf[consuming]->pfn)
>>                                   break;
>> <cut>
>
> No, I pointed following code.
> This part accesses info->page_flag_buf[i]->ready, then it accesses info->page_flag_buf[i]->pfn immediately.
> So, temp_pfn may be wrong pfn at this moment.
>
> ---
>                          for (i = 0; i < info->num_threads; i++) {
>                                  if (info->page_flag_buf[i]->ready == FLAG_UNUSED)
>                                          continue;
>                                  temp_pfn = info->page_flag_buf[i]->pfn;
> ---
>
>> The consumer will check if the pfn is changed after the page_flag_buf->ready turns to be FLAG_READY.
>> So it's not important whether setting page_flag_buf->pfn first or not.
>
> As you said, consumer checks pfn which is changed.
> So it works well.
>
>> In the other hand, even setting page_flag_buf->pfn first, if the pfn is not dumpable, the producer
>> will also reset the page_flag_buf->pfn.
>
> Thank you for your explanation.
> I didn't notice that pfn can be undumpable.
>
>>>>>
>>>>> -			buf_ready = TRUE;
>>>>> -
>>>>> -			page_data_buf[index].pfn = pfn;
>>>>> -			page_data_buf[index].ready = 1;
>>>>> +			if (pfn >= kdump_thread_args->end_pfn) {
>>>>> +				page_data_buf[index].used = 0;
>>>>> +				page_flag_buf->ready = FLAG_READY;
>>>>> +				info->current_pfn--;
>>>>> +				break;
>>>>> +			}
>>>>
>>>> This block decrements info->current_pfn without info->current_pfn_mutex.
>>>> I think this block should be moved into previous pthread_mutex_lock(info->current_pfn_mutex) block, so it can remove.
>>>>
>>
>> Why do you think it should have current_pfn_mutex?
>>
>> If pfn >= kdump_thread_args->end_pfn, info->current_pfn will always larger than
>> kdump_thread_args->end_pfn. info->current_pfn-- won't affect anything.
>>
>> The decrement operation is for cyclic mode.
>>
>>>>>
>>>>>    			dumpable = is_dumpable(
>>>>>    				info->fd_bitmap ? &bitmap_parallel : info->bitmap2,
>>>>>    				pfn,
>>>>>    				cycle);
>>>>> -			page_data_buf[index].dumpable = dumpable;
>>>>>    			if (!dumpable)
>>>>> -				goto unlock;
>>>>> +				continue;
>>>>>
>>>>>    			if (!read_pfn_parallel(fd_memory, pfn, buf,
>>>>>    					       &bitmap_memory_parallel,
>>>>> @@ -7178,11 +7225,11 @@ kdump_thread_function_cyclic(void *arg) {
>>>>>
>>>>>    			if ((info->dump_level & DL_EXCLUDE_ZERO)
>>>>>    			    && is_zero_page(buf, info->page_size)) {
>>>>> -				page_data_buf[index].zero = TRUE;
>>>>> -				goto unlock;
>>>>> +				page_flag_buf->zero = TRUE;
>>>>> +				goto next;
>>>>>    			}
>>>>
>>>> First, this code gets page_data_buf, then it gets page_flag_buf.
>>>> However, if processed pfn is zero page,
>>>> it processes next pfn while keeping page_data_buf.
>>>>
>>>> I think it should get page_flag_buf, then get page_data_buf
>>>> in order to shorten the holding period of the page_data_buf[index].mutex.
>>>>
>>
>> Do you mean the following logic?
>> 1. get the page_flag_buf first
>> 2. if the pfn is not zero page, then get the page_data_buf.
>
> Yes.
>
>> Think about the following case.
>> A producer get the page_flag_buf, and the pfn is not zero page.
>> It wants to get a page_data_buf, but there is no more page_data_buf.
>> Then ...
>
> It's not a problem.
> In not zero page case, this logic needs both page_flag_buf and page_data_buf,
> so waiting buffer is obvious when it isn't able to get page_flag_buf or page_data_buf.
>

Of course, waiting is not a problem.
But if other page_data_bufs are all used by later pfns, it will
wait forever. That's the problem.

-- 
Thanks
Zhou

>> Since there are several page_data_bufs, it's not a problem that each producer
>> will always hold a page_data_buf.
>
> It depends on the speed of consumer and producer.
> It's not possible to predict it.
>
> In zero page case, I think each producer executes more parallel theoretically
> if page_data_buf doesn't get.
>
> Thanks,
> Minoru Usui
>
>>
>> Thanks again for your comments.
>> And I will post the next version later.
>>
>> --
>> Thanks
>> Zhou
>>
>>>> Thanks,
>>>> Minoru Usui
>>>>
>>>>>
>>>>> -			page_data_buf[index].zero = FALSE;
>>>>> +			page_flag_buf->zero = FALSE;
>>>>>
>>>>>    			/*
>>>>>    			 * Compress the page data.
>>>>> @@ -7232,12 +7279,16 @@ kdump_thread_function_cyclic(void *arg) {
>>>>>    				page_data_buf[index].size  = info->page_size;
>>>>>    				memcpy(page_data_buf[index].buf, buf, info->page_size);
>>>>>    			}
>>>>> -unlock:
>>>>> -			pthread_mutex_unlock(&page_data_buf[index].mutex);
>>>>> +			page_flag_buf->index = index;
>>>>> +			buf_ready = TRUE;
>>>>> +next:
>>>>> +			page_flag_buf->ready = FLAG_READY;
>>>>> +			page_flag_buf = page_flag_buf->next;
>>>>>
>>>>>    		}
>>>>> -	}
>>>>>
>>>>> +		pthread_mutex_unlock(&page_data_buf[index].mutex);
>>>>> +	}
>>>>>    	retval = NULL;
>>>>>
>>>>>    fail:
>>>>> @@ -7265,14 +7316,15 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>>>>>    	struct page_desc pd;
>>>>>    	struct timeval tv_start;
>>>>>    	struct timeval last, new;
>>>>> -	unsigned long long consuming_pfn;
>>>>>    	pthread_t **threads = NULL;
>>>>>    	struct thread_args *kdump_thread_args = NULL;
>>>>>    	void *thread_result;
>>>>> -	int page_data_num;
>>>>> +	int page_buf_num;
>>>>>    	struct page_data *page_data_buf = NULL;
>>>>>    	int i;
>>>>>    	int index;
>>>>> +	int end_count, consuming, check_count;
>>>>> +	mdf_pfn_t current_pfn, temp_pfn;
>>>>>
>>>>>    	if (info->flag_elf_dumpfile)
>>>>>    		return FALSE;
>>>>> @@ -7319,16 +7371,11 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>>>>>    	threads = info->threads;
>>>>>    	kdump_thread_args = info->kdump_thread_args;
>>>>>
>>>>> -	page_data_num = info->num_buffers;
>>>>> +	page_buf_num = info->num_buffers;
>>>>>    	page_data_buf = info->page_data_buf;
>>>>>
>>>>> -	for (i = 0; i < page_data_num; i++) {
>>>>> -		/*
>>>>> -		 * producer will use pfn in page_data_buf to decide the
>>>>> -		 * consumed pfn
>>>>> -		 */
>>>>> -		page_data_buf[i].pfn = start_pfn - 1;
>>>>> -		page_data_buf[i].ready = 0;
>>>>> +	for (i = 0; i < page_buf_num; i++) {
>>>>> +		page_data_buf[i].used = 0;
>>>>>    		res = pthread_mutex_init(&page_data_buf[i].mutex, NULL);
>>>>>    		if (res != 0) {
>>>>>    			ERRMSG("Can't initialize mutex of page_data_buf. %s\n",
>>>>> @@ -7342,8 +7389,9 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>>>>>    		kdump_thread_args[i].len_buf_out = len_buf_out;
>>>>>    		kdump_thread_args[i].start_pfn = start_pfn;
>>>>>    		kdump_thread_args[i].end_pfn = end_pfn;
>>>>> -		kdump_thread_args[i].page_data_num = page_data_num;
>>>>> +		kdump_thread_args[i].page_buf_num = page_buf_num;
>>>>>    		kdump_thread_args[i].page_data_buf = page_data_buf;
>>>>> +		kdump_thread_args[i].page_flag_buf = info->page_flag_buf[i];
>>>>>    		kdump_thread_args[i].cycle = cycle;
>>>>>
>>>>>    		res = pthread_create(threads[i], NULL,
>>>>> @@ -7356,55 +7404,94 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>>>>>    		}
>>>>>    	}
>>>>>
>>>>> -	consuming_pfn = start_pfn;
>>>>> -	index = -1;
>>>>> +	while (1) {
>>>>> +		consuming = 0;
>>>>> +		check_count = 0;
>>>>> +		end_count = 0;
>>>>>
>>>>> -	gettimeofday(&last, NULL);
>>>>> +		/*
>>>>> +		 * The basic idea is producer producing page and consumer writing page.
>>>>> +		 * Each producer have a page_flag_buf list which is used for storing page's description.
>>>>> +		 * The size of page_flag_buf is little so it won't take too much memory.
>>>>> +		 * And all producers will share a page_data_buf array which is used for storing page's compressed data.
>>>>> +		 * The main thread is the consumer. It will find the next pfn and write it into file.
>>>>> +		 * The next pfn is smallest pfn in all page_flag_buf.
>>>>> +		 */
>>>>> +		while (1) {
>>>>> +			current_pfn = end_pfn;
>>>>>
>>>>> -	while (consuming_pfn < end_pfn) {
>>>>> -		index = consuming_pfn % page_data_num;
>>>>> +			/*
>>>>> +			 * page_flag_buf is in circular linked list.
>>>>> +			 * The array info->page_flag_buf[] records the current page_flag_buf in each thread's
>>>>> +			 * page_flag_buf list.
>>>>> +			 * consuming is used for recording in which thread the pfn is the smallest.
>>>>> +			 * current_pfn is used for recording the value of pfn when checking the pfn.
>>>>> +			 */
>>>>> +			for (i = 0; i < info->num_threads; i++) {
>>>>> +				if (info->page_flag_buf[i]->ready == FLAG_UNUSED)
>>>>> +					continue;
>>>>> +				temp_pfn = info->page_flag_buf[i]->pfn;
>>>>>
>>>>> -		gettimeofday(&new, NULL);
>>>>> -		if (new.tv_sec - last.tv_sec > WAIT_TIME) {
>>>>> -			ERRMSG("Can't get data of pfn %llx.\n", consuming_pfn);
>>>>> -			goto out;
>>>>> -		}
>>>>> +				/*
>>>>> +				 * count how many threads have reached the end.
>>>>> +				 */
>>>>> +				if (temp_pfn >= end_pfn) {
>>>>> +					end_count++;
>>>>> +					info->page_flag_buf[i]->ready = FLAG_UNUSED;
>>>>> +					continue;
>>>>> +				}
>>>>>
>>>>> -		/*
>>>>> -		 * check pfn first without mutex locked to reduce the time
>>>>> -		 * trying to lock the mutex
>>>>> -		 */
>>>>> -		if (page_data_buf[index].pfn != consuming_pfn)
>>>>> -			continue;
>>>>> +				if (current_pfn < temp_pfn)
>>>>> +					continue;
>>>>>
>>>>> -		if (pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
>>>>> -			continue;
>>>>> +				check_count++;
>>>>> +				consuming = i;
>>>>> +				current_pfn = temp_pfn;
>>>>> +			}
>>>>> +
>>>>> +			/*
>>>>> +			 * If all the threads have reached the end, we will finish writing.
>>>>> +			 */
>>>>> +			if (end_count >= info->num_threads)
>>>>> +				goto finish;
>>>>> +
>>>>> +			/*
>>>>> +			 * Since it has the probabilty that there is no page_flag_buf being ready,
>>>>> +			 * we should recheck if it happens.
>>>>> +			 */
>>>>> +			if (check_count == 0)
>>>>> +				continue;
>>>>> +
>>>>> +			/*
>>>>> +			 * When we check the pfn in page_flag_buf, it may be being produced.
>>>>> +			 * So we should wait until it is ready to use. And if the pfn is
>>>>> +			 * different from the value when we check, we should rechoose the buf.
>>>>> +			 */
>>>>> +			gettimeofday(&last, NULL);
>>>>> +			while (info->page_flag_buf[consuming]->ready != FLAG_READY) {
>>>>> +				gettimeofday(&new, NULL);
>>>>> +				if (new.tv_sec - last.tv_sec > WAIT_TIME) {
>>>>> +					ERRMSG("Can't get data of pfn.\n");
>>>>> +					goto out;
>>>>> +				}
>>>>> +			}
>>>>>
>>>>> -		/* check whether the found one is ready to be consumed */
>>>>> -		if (page_data_buf[index].pfn != consuming_pfn ||
>>>>> -		    page_data_buf[index].ready != 1) {
>>>>> -			goto unlock;
>>>>> +			if (current_pfn == info->page_flag_buf[consuming]->pfn)
>>>>> +				break;
>>>>>    		}
>>>>>
>>>>>    		if ((num_dumped % per) == 0)
>>>>>    			print_progress(PROGRESS_COPY, num_dumped, info->num_dumpable);
>>>>>
>>>>> -		/* next pfn is found, refresh last here */
>>>>> -		last = new;
>>>>> -		consuming_pfn++;
>>>>> -		info->consumed_pfn++;
>>>>> -		page_data_buf[index].ready = 0;
>>>>> -
>>>>> -		if (page_data_buf[index].dumpable == FALSE)
>>>>> -			goto unlock;
>>>>> -
>>>>>    		num_dumped++;
>>>>>
>>>>> -		if (page_data_buf[index].zero == TRUE) {
>>>>> +
>>>>> +		if (info->page_flag_buf[consuming]->zero == TRUE) {
>>>>>    			if (!write_cache(cd_header, pd_zero, sizeof(page_desc_t)))
>>>>>    				goto out;
>>>>>    			pfn_zero++;
>>>>>    		} else {
>>>>> +			index = info->page_flag_buf[consuming]->index;
>>>>>    			pd.flags      = page_data_buf[index].flags;
>>>>>    			pd.size       = page_data_buf[index].size;
>>>>>    			pd.page_flags = 0;
>>>>> @@ -7420,12 +7507,12 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>>>>>    			 */
>>>>>    			if (!write_cache(cd_page, page_data_buf[index].buf, pd.size))
>>>>>    				goto out;
>>>>> -
>>>>> +			page_data_buf[index].used = 0;
>>>>>    		}
>>>>> -unlock:
>>>>> -		pthread_mutex_unlock(&page_data_buf[index].mutex);
>>>>> +		info->page_flag_buf[consuming]->ready = FLAG_UNUSED;
>>>>> +		info->page_flag_buf[consuming] = info->page_flag_buf[consuming]->next;
>>>>>    	}
>>>>> -
>>>>> +finish:
>>>>>    	ret = TRUE;
>>>>>    	/*
>>>>>    	 * print [100 %]
>>>>> @@ -7464,7 +7551,7 @@ out:
>>>>>    	}
>>>>>
>>>>>    	if (page_data_buf != NULL) {
>>>>> -		for (i = 0; i < page_data_num; i++) {
>>>>> +		for (i = 0; i < page_buf_num; i++) {
>>>>>    			pthread_mutex_destroy(&page_data_buf[i].mutex);
>>>>>    		}
>>>>>    	}
>>>>> @@ -7564,6 +7651,7 @@ write_kdump_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_pag
>>>>>    		num_dumped++;
>>>>>    		if (!read_pfn(pfn, buf))
>>>>>    			goto out;
>>>>> +
>>>>>    		filter_data_buffer(buf, pfn_to_paddr(pfn), info->page_size);
>>>>>
>>>>>    		/*
>>>>> diff --git a/makedumpfile.h b/makedumpfile.h
>>>>> index e0b5bbf..8a9a5b2 100644
>>>>> --- a/makedumpfile.h
>>>>> +++ b/makedumpfile.h
>>>>> @@ -977,7 +977,7 @@ typedef unsigned long long int ulonglong;
>>>>>    #define PAGE_DATA_NUM	(50)
>>>>>    #define WAIT_TIME	(60 * 10)
>>>>>    #define PTHREAD_FAIL	((void *)-2)
>>>>> -#define NUM_BUFFERS	(50)
>>>>> +#define NUM_BUFFERS	(20)
>>>>>
>>>>>    struct mmap_cache {
>>>>>    	char	*mmap_buf;
>>>>> @@ -985,28 +985,36 @@ struct mmap_cache {
>>>>>    	off_t   mmap_end_offset;
>>>>>    };
>>>>>
>>>>> +enum {
>>>>> +	FLAG_UNUSED,
>>>>> +	FLAG_READY,
>>>>> +	FLAG_FILLING
>>>>> +};
>>>>> +struct page_flag {
>>>>> +	mdf_pfn_t pfn;
>>>>> +	char zero;
>>>>> +	char ready;
>>>>> +	short index;
>>>>> +	struct page_flag *next;
>>>>> +};
>>>>> +
>>>>>    struct page_data
>>>>>    {
>>>>> -	mdf_pfn_t pfn;
>>>>> -	int dumpable;
>>>>> -	int zero;
>>>>> -	unsigned int flags;
>>>>> +	pthread_mutex_t mutex;
>>>>>    	long size;
>>>>>    	unsigned char *buf;
>>>>> -	pthread_mutex_t mutex;
>>>>> -	/*
>>>>> -	 * whether the page_data is ready to be consumed
>>>>> -	 */
>>>>> -	int ready;
>>>>> +	int flags;
>>>>> +	int used;
>>>>>    };
>>>>>
>>>>>    struct thread_args {
>>>>>    	int thread_num;
>>>>>    	unsigned long len_buf_out;
>>>>>    	mdf_pfn_t start_pfn, end_pfn;
>>>>> -	int page_data_num;
>>>>> +	int page_buf_num;
>>>>>    	struct cycle *cycle;
>>>>>    	struct page_data *page_data_buf;
>>>>> +	struct page_flag *page_flag_buf;
>>>>>    };
>>>>>
>>>>>    /*
>>>>> @@ -1295,6 +1303,7 @@ struct DumpInfo {
>>>>>    	pthread_t **threads;
>>>>>    	struct thread_args *kdump_thread_args;
>>>>>    	struct page_data *page_data_buf;
>>>>> +	struct page_flag **page_flag_buf;
>>>>>    	pthread_rwlock_t usemmap_rwlock;
>>>>>    	mdf_pfn_t current_pfn;
>>>>>    	pthread_mutex_t current_pfn_mutex;
>>>>> --
>>>>> 1.8.3.1
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> kexec mailing list
>>>>> kexec@lists.infradead.org
>>>>> http://lists.infradead.org/mailman/listinfo/kexec
>>>>
>>>> _______________________________________________
>>>> kexec mailing list
>>>> kexec@lists.infradead.org
>>>> http://lists.infradead.org/mailman/listinfo/kexec
>>>
>>>
>>




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Re: [PATCH v1] Improve the performance of --num-threads -d 31

[Minoru Usui]

Hi,

> -----Original Message-----
> From: "Zhou, Wenjian/周文剑" [mailto:zhouwj-fnst@cn.fujitsu.com]
> Sent: Tuesday, February 23, 2016 12:53 PM
> To: Usui Minoru(碓井 成) <min-usui@ti.jp.nec.com>; kexec@lists.infradead.org
> Subject: Re: [PATCH v1] Improve the performance of --num-threads -d 31
> 
> On 02/23/2016 10:16 AM, Minoru Usui wrote:
> > Hello Zhou
> >
> > I'm sorry for late reply, too.
> >
> >> -----Original Message-----
> >> From: "Zhou, Wenjian/周文剑" [mailto:zhouwj-fnst@cn.fujitsu.com]
> >> Sent: Monday, February 15, 2016 11:15 AM
> >> To: Usui Minoru(碓井 成) <min-usui@ti.jp.nec.com>; kexec@lists.infradead.org
> >> Subject: Re: [PATCH v1] Improve the performance of --num-threads -d 31
> >>
> >> Hello Usui,
> >>
> >> Thanks very much for your comments.
> >> And sorry for the late reply.
> >>
> >> See below.
> >>
> >> On 02/08/2016 01:00 PM, Minoru Usui wrote:
> >>> Hello,
> >>>
> >>>> -----Original Message-----
> >>>> From: kexec [mailto:kexec-bounces@lists.infradead.org] On Behalf Of Minoru Usui
> >>>> Sent: Thursday, February 04, 2016 8:52 AM
> >>>> To: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>; kexec@lists.infradead.org
> >>>> Subject: Re: [PATCH v1] Improve the performance of --num-threads -d 31
> >>>>
> >>>> Hi, Zhou
> >>>>
> >>>> I have some comments.
> >>>> I'm sorry if I have misunderstood your code.
> >>>>
> >>>>> -----Original Message-----
> >>>>> From: kexec [mailto:kexec-bounces@lists.infradead.org] On Behalf Of Zhou Wenjian
> >>>>> Sent: Monday, February 01, 2016 3:22 PM
> >>>>> To: kexec@lists.infradead.org
> >>>>> Subject: [PATCH v1] Improve the performance of --num-threads -d 31
> >>>>>
> >>>>> v1:
> >>>>>           1. change page_flag.ready's value to enum
> >>>>>           2. change the patch description
> >>>>>           3. cleanup some codes
> >>>>> 	4. fix a bug in cyclic mode
> >>>>>
> >>>>> multi-threads implementation will introduce extra cost when handling
> >>>>> each page. The origin implementation will also do the extra work for
> >>>>> filtered pages. So there is a big performance degradation in
> >>>>> --num-threads -d 31.
> >>>>> The new implementation won't do the extra work for filtered pages any
> >>>>> more. So the performance of -d 31 is close to that of serial processing.
> >>>>>
> >>>>> The new implementation is just like the following:
> >>>>>           * The basic idea is producer producing page and consumer writing page.
> >>>>>           * Each producer have a page_flag_buf list which is used for storing
> >>>>>             page's description.
> >>>>>           * The size of page_flag_buf is little so it won't take too much memory.
> >>>>>           * And all producers will share a page_data_buf array which is
> >>>>>             used for storing page's compressed data.
> >>>>>           * The main thread is the consumer. It will find the next pfn and write
> >>>>>             it into file.
> >>>>>           * The next pfn is smallest pfn in all page_flag_buf.
> >>>>>
> >>>>> Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>
> >>>>> ---
> >>>>>    makedumpfile.c | 258 ++++++++++++++++++++++++++++++++++++++-------------------
> >>>>>    makedumpfile.h |  31 ++++---
> >>>>>    2 files changed, 193 insertions(+), 96 deletions(-)
> >>>>>
> >>>>> diff --git a/makedumpfile.c b/makedumpfile.c
> >>>>> index fa0b779..0ecd065 100644
> >>>>> --- a/makedumpfile.c
> >>>>> +++ b/makedumpfile.c
> >>>>> @@ -3483,7 +3483,8 @@ initial_for_parallel()
> >>>>>    	unsigned long page_data_buf_size;
> >>>>>    	unsigned long limit_size;
> >>>>>    	int page_data_num;
> >>>>> -	int i;
> >>>>> +	struct page_flag *current;
> >>>>> +	int i, j;
> >>>>>
> >>>>>    	len_buf_out = calculate_len_buf_out(info->page_size);
> >>>>>
> >>>>> @@ -3562,8 +3563,10 @@ initial_for_parallel()
> >>>>>    		      - MAP_REGION * info->num_threads) * 0.6;
> >>>>>
> >>>>>    	page_data_num = limit_size / page_data_buf_size;
> >>>>> +	info->num_buffers = 3 * info->num_threads;
> >>>>>
> >>>>> -	info->num_buffers = MIN(NUM_BUFFERS, page_data_num);
> >>>>> +	info->num_buffers = MAX(info->num_buffers, NUM_BUFFERS);
> >>>>> +	info->num_buffers = MIN(info->num_buffers, page_data_num);
> >>>>>
> >>>>>    	DEBUG_MSG("Number of struct page_data for produce/consume: %d\n",
> >>>>>    			info->num_buffers);
> >>>>> @@ -3588,6 +3591,36 @@ initial_for_parallel()
> >>>>>    	}
> >>>>>
> >>>>>    	/*
> >>>>> +	 * initial page_flag for each thread
> >>>>> +	 */
> >>>>> +	if ((info->page_flag_buf = malloc(sizeof(void *) * info->num_threads))
> >>>>> +	    == NULL) {
> >>>>> +		MSG("Can't allocate memory for page_flag_buf. %s\n",
> >>>>> +				strerror(errno));
> >>>>> +		return FALSE;
> >>>>> +	}
> >>>>> +	memset(info->page_flag_buf, 0, sizeof(void *) * info->num_threads);
> >>>>> +
> >>>>> +	for (i = 0; i < info->num_threads; i++) {
> >>>>> +		if ((info->page_flag_buf[i] = malloc(sizeof(struct page_flag))) == NULL) {
> >>>>
> >>>> Fist element of struct page_flag in circular list is allocated by malloc(),
> >>>> but other elements are allocated by calloc().(see below)
> >>>> I think both elements should be allocated by calloc().
> >>>>
> >>
> >> Yes, you are right.
> >> I have made a mistake.
> >>
> >>>>> +			MSG("Can't allocate memory for page_flag_buf. %s\n",
> >>>>> +				strerror(errno));
> >>>>> +			return FALSE;
> >>>>> +		}
> >>>>> +		current = info->page_flag_buf[i];
> >>>>> +
> >>>>> +		for (j = 1; j < NUM_BUFFERS; j++) {
> >>>>> +			if ((current->next = calloc(0, sizeof(struct page_flag))) == NULL) {
> >>>>> +				MSG("Can't allocate memory for data of page_data_buf. %s\n",
> >>>>> +					strerror(errno));
> >>>>> +				return FALSE;
> >>>>> +			}
> >>>>
> >>>>
> >>>> First argument of calloc() should be 1, not 0.
> >>>> And there is typo in error message.
> >>>> Allocated element is not page_data_buf.
> >>>>
> >>
> >> I agree.
> >>
> >>>>> +			current = current->next;
> >>>>> +		}
> >>>>> +		current->next = info->page_flag_buf[i];
> >>>>> +	}
> >>>>> +
> >>>>> +	/*
> >>>>>    	 * initial fd_memory for threads
> >>>>>    	 */
> >>>>>    	for (i = 0; i < info->num_threads; i++) {
> >>>>> @@ -3612,7 +3645,8 @@ initial_for_parallel()
> >>>>>    void
> >>>>>    free_for_parallel()
> >>>>>    {
> >>>>> -	int i;
> >>>>> +	int i, j;
> >>>>> +	struct page_flag *current;
> >>>>>
> >>>>>    	if (info->threads != NULL) {
> >>>>>    		for (i = 0; i < info->num_threads; i++) {
> >>>>> @@ -3655,6 +3689,19 @@ free_for_parallel()
> >>>>>    		free(info->page_data_buf);
> >>>>>    	}
> >>>>>
> >>>>> +	if (info->page_flag_buf != NULL) {
> >>>>> +		for (i = 0; i < info->num_threads; i++) {
> >>>>> +			for (j = 0; j < NUM_BUFFERS; j++) {
> >>>>> +				if (info->page_flag_buf[i] != NULL) {
> >>>>> +					current = info->page_flag_buf[i];
> >>>>> +					info->page_flag_buf[i] = current->next;
> >>>>> +					free(current);
> >>>>> +				}
> >>>>> +			}
> >>>>> +		}
> >>>>> +		free(info->page_flag_buf);
> >>>>> +	}
> >>>>> +
> >>>>>    	if (info->parallel_info == NULL)
> >>>>>    		return;
> >>>>>
> >>>>> @@ -7076,10 +7123,10 @@ kdump_thread_function_cyclic(void *arg) {
> >>>>>    	void *retval = PTHREAD_FAIL;
> >>>>>    	struct thread_args *kdump_thread_args = (struct thread_args *)arg;
> >>>>>    	struct page_data *page_data_buf = kdump_thread_args->page_data_buf;
> >>>>> +	struct page_flag *page_flag_buf = kdump_thread_args->page_flag_buf;
> >>>>>    	struct cycle *cycle = kdump_thread_args->cycle;
> >>>>> -	int page_data_num = kdump_thread_args->page_data_num;
> >>>>>    	mdf_pfn_t pfn;
> >>>>> -	int index;
> >>>>> +	int index = kdump_thread_args->thread_num;
> >>>>>    	int buf_ready;
> >>>>>    	int dumpable;
> >>>>>    	int fd_memory = 0;
> >>>>> @@ -7125,47 +7172,47 @@ kdump_thread_function_cyclic(void *arg) {
> >>>>>    						kdump_thread_args->thread_num);
> >>>>>    	}
> >>>>>
> >>>>> -	while (1) {
> >>>>> -		/* get next pfn */
> >>>>> -		pthread_mutex_lock(&info->current_pfn_mutex);
> >>>>> -		pfn = info->current_pfn;
> >>>>> -		info->current_pfn++;
> >>>>> -		pthread_mutex_unlock(&info->current_pfn_mutex);
> >>>>> +	/*
> >>>>> +	 * filtered page won't take anything
> >>>>> +	 * unfiltered zero page will only take a page_flag_buf
> >>>>> +	 * unfiltered non-zero page will take a page_flag_buf and a page_data_buf
> >>>>> +	 */
> >>>>> +	while (page_flag_buf->pfn < kdump_thread_args->end_pfn) {
> >>>>
> >>>> At first, page_flag_buf->pfn is not initialized.
> >>>> I think this block should be replaced with the following code.
> >>>>
> >>>> ===
> >>>>     do {
> >>>>       :
> >>>>     } while(page_flag_buf->pfn < kdump_thread_args->end_pfn)
> >>>> ===
> >>>
> >>> I'm sorry, above suggestion is meaningless in terms of page_flag_buf->pfn is uninitialized.
> >>> It should be replaced like following.
> >>>
> >>> ===
> >>>     while (1) {
> >>>       :
> >>>       while (buf_ready == FALSE) {
> >>>          :
> >>>         if (pfn >= kdump_thread_args->end_pfn) {
> >>>            :
> >>>           goto finish;
> >>>         }
> >>>         :
> >>>       }
> >>>       :
> >>>     }
> >>> finish:
> >>> ===
> >>>
> >>
> >> page_flag_buf is allocated by calloc().
> >> The page_flag_buf->pfn's value is 0.
> >> So I think it is not necessary to modify the code.
> >>
> >>> Thanks,
> >>> Minoru Usui
> >>>
> >>>
> >>>>> +		buf_ready = FALSE;
> >>>>>
> >>>>> -		if (pfn >= kdump_thread_args->end_pfn)
> >>>>> -			break;
> >>>>> +		while (page_data_buf[index].used != 0 ||
> >>>>> +				pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
> >>>>> +			index = (index + 1) % info->num_buffers;
> >>>>>
> >>>>> -		index = -1;
> >>>>> -		buf_ready = FALSE;
> >>>>> +		page_data_buf[index].used = 1;
> >>>>
> >>>> "1" is a magic number.
> >>>> It should be changed TRUE or FALSE.
> >>>>
> >>
> >> I see.
> >>
> >>>>>    		while (buf_ready == FALSE) {
> >>>>>    			pthread_testcancel();
> >>>>> -
> >>>>> -			index = pfn % page_data_num;
> >>>>> -
> >>>>> -			if (pfn - info->consumed_pfn > info->num_buffers)
> >>>>> +			if (page_flag_buf->ready == FLAG_READY)
> >>>>>    				continue;
> >>>>
> >>>> At first, page_flag_buf->ready is uninitialized, too.
> >>>> Should it be initialized in head part of this function, even if FLAG_UNUSED is defined 0?
> >>>>
> >>>>
> >>
> >> The same topic as the page_flag_buf is allocated by calloc().
> >>
> >>>>>
> >>>>> -			if (page_data_buf[index].ready != 0)
> >>>>> -				continue;
> >>>>> -
> >>>>> -			pthread_mutex_lock(&page_data_buf[index].mutex);
> >>>>> +			/* get next pfn */
> >>>>> +			pthread_mutex_lock(&info->current_pfn_mutex);
> >>>>> +			pfn = info->current_pfn;
> >>>>> +			info->current_pfn++;
> >>>>> +			page_flag_buf->ready = FLAG_FILLING;
> >>>>> +			pthread_mutex_unlock(&info->current_pfn_mutex);
> >>>>>
> >>>>> -			if (page_data_buf[index].ready != 0)
> >>>>> -				goto unlock;
> >>>>> +			page_flag_buf->pfn = pfn;
> >>>>
> >>>> It set FLAG_FILLING to page_flag_buf->ready before setting pfn to page_flag_buf->pfn.
> >>>> But consumer gets page_flag_buf->pfn after checking page_flag_buf->ready != FLAG_UNUSED
> >>>> in getting minimum pfn of each thread block.
> >>>> Should it set page_flag_buf->pfn first?
> >>>>
> >>
> >> Have you noticed the following code in the consumer?
> >> <cut>
> >>                           if (current_pfn == info->page_flag_buf[consuming]->pfn)
> >>                                   break;
> >> <cut>
> >
> > No, I pointed following code.
> > This part accesses info->page_flag_buf[i]->ready, then it accesses info->page_flag_buf[i]->pfn immediately.
> > So, temp_pfn may be wrong pfn at this moment.
> >
> > ---
> >                          for (i = 0; i < info->num_threads; i++) {
> >                                  if (info->page_flag_buf[i]->ready == FLAG_UNUSED)
> >                                          continue;
> >                                  temp_pfn = info->page_flag_buf[i]->pfn;
> > ---
> >
> >> The consumer will check if the pfn is changed after the page_flag_buf->ready turns to be FLAG_READY.
> >> So it's not important whether setting page_flag_buf->pfn first or not.
> >
> > As you said, consumer checks pfn which is changed.
> > So it works well.
> >
> >> In the other hand, even setting page_flag_buf->pfn first, if the pfn is not dumpable, the producer
> >> will also reset the page_flag_buf->pfn.
> >
> > Thank you for your explanation.
> > I didn't notice that pfn can be undumpable.
> >
> >>>>>
> >>>>> -			buf_ready = TRUE;
> >>>>> -
> >>>>> -			page_data_buf[index].pfn = pfn;
> >>>>> -			page_data_buf[index].ready = 1;
> >>>>> +			if (pfn >= kdump_thread_args->end_pfn) {
> >>>>> +				page_data_buf[index].used = 0;
> >>>>> +				page_flag_buf->ready = FLAG_READY;
> >>>>> +				info->current_pfn--;
> >>>>> +				break;
> >>>>> +			}
> >>>>
> >>>> This block decrements info->current_pfn without info->current_pfn_mutex.
> >>>> I think this block should be moved into previous pthread_mutex_lock(info->current_pfn_mutex) block, so it can remove.
> >>>>
> >>
> >> Why do you think it should have current_pfn_mutex?
> >>
> >> If pfn >= kdump_thread_args->end_pfn, info->current_pfn will always larger than
> >> kdump_thread_args->end_pfn. info->current_pfn-- won't affect anything.
> >>
> >> The decrement operation is for cyclic mode.
> >>
> >>>>>
> >>>>>    			dumpable = is_dumpable(
> >>>>>    				info->fd_bitmap ? &bitmap_parallel : info->bitmap2,
> >>>>>    				pfn,
> >>>>>    				cycle);
> >>>>> -			page_data_buf[index].dumpable = dumpable;
> >>>>>    			if (!dumpable)
> >>>>> -				goto unlock;
> >>>>> +				continue;
> >>>>>
> >>>>>    			if (!read_pfn_parallel(fd_memory, pfn, buf,
> >>>>>    					       &bitmap_memory_parallel,
> >>>>> @@ -7178,11 +7225,11 @@ kdump_thread_function_cyclic(void *arg) {
> >>>>>
> >>>>>    			if ((info->dump_level & DL_EXCLUDE_ZERO)
> >>>>>    			    && is_zero_page(buf, info->page_size)) {
> >>>>> -				page_data_buf[index].zero = TRUE;
> >>>>> -				goto unlock;
> >>>>> +				page_flag_buf->zero = TRUE;
> >>>>> +				goto next;
> >>>>>    			}
> >>>>
> >>>> First, this code gets page_data_buf, then it gets page_flag_buf.
> >>>> However, if processed pfn is zero page,
> >>>> it processes next pfn while keeping page_data_buf.
> >>>>
> >>>> I think it should get page_flag_buf, then get page_data_buf
> >>>> in order to shorten the holding period of the page_data_buf[index].mutex.
> >>>>
> >>
> >> Do you mean the following logic?
> >> 1. get the page_flag_buf first
> >> 2. if the pfn is not zero page, then get the page_data_buf.
> >
> > Yes.
> >
> >> Think about the following case.
> >> A producer get the page_flag_buf, and the pfn is not zero page.
> >> It wants to get a page_data_buf, but there is no more page_data_buf.
> >> Then ...
> >
> > It's not a problem.
> > In not zero page case, this logic needs both page_flag_buf and page_data_buf,
> > so waiting buffer is obvious when it isn't able to get page_flag_buf or page_data_buf.
> >
> 
> Of course, waiting is not a problem.
> But if other page_data_bufs are all used by later pfns, it will
> wait forever. That's the problem.

I understand.
Thank you for your explanation.

Minoru Usui

> --
> Thanks
> Zhou
> 
> >> Since there are several page_data_bufs, it's not a problem that each producer
> >> will always hold a page_data_buf.
> >
> > It depends on the speed of consumer and producer.
> > It's not possible to predict it.
> >
> > In zero page case, I think each producer executes more parallel theoretically
> > if page_data_buf doesn't get.
> >
> > Thanks,
> > Minoru Usui
> >
> >>
> >> Thanks again for your comments.
> >> And I will post the next version later.
> >>
> >> --
> >> Thanks
> >> Zhou
> >>
> >>>> Thanks,
> >>>> Minoru Usui
> >>>>
> >>>>>
> >>>>> -			page_data_buf[index].zero = FALSE;
> >>>>> +			page_flag_buf->zero = FALSE;
> >>>>>
> >>>>>    			/*
> >>>>>    			 * Compress the page data.
> >>>>> @@ -7232,12 +7279,16 @@ kdump_thread_function_cyclic(void *arg) {
> >>>>>    				page_data_buf[index].size  = info->page_size;
> >>>>>    				memcpy(page_data_buf[index].buf, buf, info->page_size);
> >>>>>    			}
> >>>>> -unlock:
> >>>>> -			pthread_mutex_unlock(&page_data_buf[index].mutex);
> >>>>> +			page_flag_buf->index = index;
> >>>>> +			buf_ready = TRUE;
> >>>>> +next:
> >>>>> +			page_flag_buf->ready = FLAG_READY;
> >>>>> +			page_flag_buf = page_flag_buf->next;
> >>>>>
> >>>>>    		}
> >>>>> -	}
> >>>>>
> >>>>> +		pthread_mutex_unlock(&page_data_buf[index].mutex);
> >>>>> +	}
> >>>>>    	retval = NULL;
> >>>>>
> >>>>>    fail:
> >>>>> @@ -7265,14 +7316,15 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >>>>>    	struct page_desc pd;
> >>>>>    	struct timeval tv_start;
> >>>>>    	struct timeval last, new;
> >>>>> -	unsigned long long consuming_pfn;
> >>>>>    	pthread_t **threads = NULL;
> >>>>>    	struct thread_args *kdump_thread_args = NULL;
> >>>>>    	void *thread_result;
> >>>>> -	int page_data_num;
> >>>>> +	int page_buf_num;
> >>>>>    	struct page_data *page_data_buf = NULL;
> >>>>>    	int i;
> >>>>>    	int index;
> >>>>> +	int end_count, consuming, check_count;
> >>>>> +	mdf_pfn_t current_pfn, temp_pfn;
> >>>>>
> >>>>>    	if (info->flag_elf_dumpfile)
> >>>>>    		return FALSE;
> >>>>> @@ -7319,16 +7371,11 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >>>>>    	threads = info->threads;
> >>>>>    	kdump_thread_args = info->kdump_thread_args;
> >>>>>
> >>>>> -	page_data_num = info->num_buffers;
> >>>>> +	page_buf_num = info->num_buffers;
> >>>>>    	page_data_buf = info->page_data_buf;
> >>>>>
> >>>>> -	for (i = 0; i < page_data_num; i++) {
> >>>>> -		/*
> >>>>> -		 * producer will use pfn in page_data_buf to decide the
> >>>>> -		 * consumed pfn
> >>>>> -		 */
> >>>>> -		page_data_buf[i].pfn = start_pfn - 1;
> >>>>> -		page_data_buf[i].ready = 0;
> >>>>> +	for (i = 0; i < page_buf_num; i++) {
> >>>>> +		page_data_buf[i].used = 0;
> >>>>>    		res = pthread_mutex_init(&page_data_buf[i].mutex, NULL);
> >>>>>    		if (res != 0) {
> >>>>>    			ERRMSG("Can't initialize mutex of page_data_buf. %s\n",
> >>>>> @@ -7342,8 +7389,9 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >>>>>    		kdump_thread_args[i].len_buf_out = len_buf_out;
> >>>>>    		kdump_thread_args[i].start_pfn = start_pfn;
> >>>>>    		kdump_thread_args[i].end_pfn = end_pfn;
> >>>>> -		kdump_thread_args[i].page_data_num = page_data_num;
> >>>>> +		kdump_thread_args[i].page_buf_num = page_buf_num;
> >>>>>    		kdump_thread_args[i].page_data_buf = page_data_buf;
> >>>>> +		kdump_thread_args[i].page_flag_buf = info->page_flag_buf[i];
> >>>>>    		kdump_thread_args[i].cycle = cycle;
> >>>>>
> >>>>>    		res = pthread_create(threads[i], NULL,
> >>>>> @@ -7356,55 +7404,94 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >>>>>    		}
> >>>>>    	}
> >>>>>
> >>>>> -	consuming_pfn = start_pfn;
> >>>>> -	index = -1;
> >>>>> +	while (1) {
> >>>>> +		consuming = 0;
> >>>>> +		check_count = 0;
> >>>>> +		end_count = 0;
> >>>>>
> >>>>> -	gettimeofday(&last, NULL);
> >>>>> +		/*
> >>>>> +		 * The basic idea is producer producing page and consumer writing page.
> >>>>> +		 * Each producer have a page_flag_buf list which is used for storing page's description.
> >>>>> +		 * The size of page_flag_buf is little so it won't take too much memory.
> >>>>> +		 * And all producers will share a page_data_buf array which is used for storing page's compressed data.
> >>>>> +		 * The main thread is the consumer. It will find the next pfn and write it into file.
> >>>>> +		 * The next pfn is smallest pfn in all page_flag_buf.
> >>>>> +		 */
> >>>>> +		while (1) {
> >>>>> +			current_pfn = end_pfn;
> >>>>>
> >>>>> -	while (consuming_pfn < end_pfn) {
> >>>>> -		index = consuming_pfn % page_data_num;
> >>>>> +			/*
> >>>>> +			 * page_flag_buf is in circular linked list.
> >>>>> +			 * The array info->page_flag_buf[] records the current page_flag_buf in each thread's
> >>>>> +			 * page_flag_buf list.
> >>>>> +			 * consuming is used for recording in which thread the pfn is the smallest.
> >>>>> +			 * current_pfn is used for recording the value of pfn when checking the pfn.
> >>>>> +			 */
> >>>>> +			for (i = 0; i < info->num_threads; i++) {
> >>>>> +				if (info->page_flag_buf[i]->ready == FLAG_UNUSED)
> >>>>> +					continue;
> >>>>> +				temp_pfn = info->page_flag_buf[i]->pfn;
> >>>>>
> >>>>> -		gettimeofday(&new, NULL);
> >>>>> -		if (new.tv_sec - last.tv_sec > WAIT_TIME) {
> >>>>> -			ERRMSG("Can't get data of pfn %llx.\n", consuming_pfn);
> >>>>> -			goto out;
> >>>>> -		}
> >>>>> +				/*
> >>>>> +				 * count how many threads have reached the end.
> >>>>> +				 */
> >>>>> +				if (temp_pfn >= end_pfn) {
> >>>>> +					end_count++;
> >>>>> +					info->page_flag_buf[i]->ready = FLAG_UNUSED;
> >>>>> +					continue;
> >>>>> +				}
> >>>>>
> >>>>> -		/*
> >>>>> -		 * check pfn first without mutex locked to reduce the time
> >>>>> -		 * trying to lock the mutex
> >>>>> -		 */
> >>>>> -		if (page_data_buf[index].pfn != consuming_pfn)
> >>>>> -			continue;
> >>>>> +				if (current_pfn < temp_pfn)
> >>>>> +					continue;
> >>>>>
> >>>>> -		if (pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
> >>>>> -			continue;
> >>>>> +				check_count++;
> >>>>> +				consuming = i;
> >>>>> +				current_pfn = temp_pfn;
> >>>>> +			}
> >>>>> +
> >>>>> +			/*
> >>>>> +			 * If all the threads have reached the end, we will finish writing.
> >>>>> +			 */
> >>>>> +			if (end_count >= info->num_threads)
> >>>>> +				goto finish;
> >>>>> +
> >>>>> +			/*
> >>>>> +			 * Since it has the probabilty that there is no page_flag_buf being ready,
> >>>>> +			 * we should recheck if it happens.
> >>>>> +			 */
> >>>>> +			if (check_count == 0)
> >>>>> +				continue;
> >>>>> +
> >>>>> +			/*
> >>>>> +			 * When we check the pfn in page_flag_buf, it may be being produced.
> >>>>> +			 * So we should wait until it is ready to use. And if the pfn is
> >>>>> +			 * different from the value when we check, we should rechoose the buf.
> >>>>> +			 */
> >>>>> +			gettimeofday(&last, NULL);
> >>>>> +			while (info->page_flag_buf[consuming]->ready != FLAG_READY) {
> >>>>> +				gettimeofday(&new, NULL);
> >>>>> +				if (new.tv_sec - last.tv_sec > WAIT_TIME) {
> >>>>> +					ERRMSG("Can't get data of pfn.\n");
> >>>>> +					goto out;
> >>>>> +				}
> >>>>> +			}
> >>>>>
> >>>>> -		/* check whether the found one is ready to be consumed */
> >>>>> -		if (page_data_buf[index].pfn != consuming_pfn ||
> >>>>> -		    page_data_buf[index].ready != 1) {
> >>>>> -			goto unlock;
> >>>>> +			if (current_pfn == info->page_flag_buf[consuming]->pfn)
> >>>>> +				break;
> >>>>>    		}
> >>>>>
> >>>>>    		if ((num_dumped % per) == 0)
> >>>>>    			print_progress(PROGRESS_COPY, num_dumped, info->num_dumpable);
> >>>>>
> >>>>> -		/* next pfn is found, refresh last here */
> >>>>> -		last = new;
> >>>>> -		consuming_pfn++;
> >>>>> -		info->consumed_pfn++;
> >>>>> -		page_data_buf[index].ready = 0;
> >>>>> -
> >>>>> -		if (page_data_buf[index].dumpable == FALSE)
> >>>>> -			goto unlock;
> >>>>> -
> >>>>>    		num_dumped++;
> >>>>>
> >>>>> -		if (page_data_buf[index].zero == TRUE) {
> >>>>> +
> >>>>> +		if (info->page_flag_buf[consuming]->zero == TRUE) {
> >>>>>    			if (!write_cache(cd_header, pd_zero, sizeof(page_desc_t)))
> >>>>>    				goto out;
> >>>>>    			pfn_zero++;
> >>>>>    		} else {
> >>>>> +			index = info->page_flag_buf[consuming]->index;
> >>>>>    			pd.flags      = page_data_buf[index].flags;
> >>>>>    			pd.size       = page_data_buf[index].size;
> >>>>>    			pd.page_flags = 0;
> >>>>> @@ -7420,12 +7507,12 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >>>>>    			 */
> >>>>>    			if (!write_cache(cd_page, page_data_buf[index].buf, pd.size))
> >>>>>    				goto out;
> >>>>> -
> >>>>> +			page_data_buf[index].used = 0;
> >>>>>    		}
> >>>>> -unlock:
> >>>>> -		pthread_mutex_unlock(&page_data_buf[index].mutex);
> >>>>> +		info->page_flag_buf[consuming]->ready = FLAG_UNUSED;
> >>>>> +		info->page_flag_buf[consuming] = info->page_flag_buf[consuming]->next;
> >>>>>    	}
> >>>>> -
> >>>>> +finish:
> >>>>>    	ret = TRUE;
> >>>>>    	/*
> >>>>>    	 * print [100 %]
> >>>>> @@ -7464,7 +7551,7 @@ out:
> >>>>>    	}
> >>>>>
> >>>>>    	if (page_data_buf != NULL) {
> >>>>> -		for (i = 0; i < page_data_num; i++) {
> >>>>> +		for (i = 0; i < page_buf_num; i++) {
> >>>>>    			pthread_mutex_destroy(&page_data_buf[i].mutex);
> >>>>>    		}
> >>>>>    	}
> >>>>> @@ -7564,6 +7651,7 @@ write_kdump_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_pag
> >>>>>    		num_dumped++;
> >>>>>    		if (!read_pfn(pfn, buf))
> >>>>>    			goto out;
> >>>>> +
> >>>>>    		filter_data_buffer(buf, pfn_to_paddr(pfn), info->page_size);
> >>>>>
> >>>>>    		/*
> >>>>> diff --git a/makedumpfile.h b/makedumpfile.h
> >>>>> index e0b5bbf..8a9a5b2 100644
> >>>>> --- a/makedumpfile.h
> >>>>> +++ b/makedumpfile.h
> >>>>> @@ -977,7 +977,7 @@ typedef unsigned long long int ulonglong;
> >>>>>    #define PAGE_DATA_NUM	(50)
> >>>>>    #define WAIT_TIME	(60 * 10)
> >>>>>    #define PTHREAD_FAIL	((void *)-2)
> >>>>> -#define NUM_BUFFERS	(50)
> >>>>> +#define NUM_BUFFERS	(20)
> >>>>>
> >>>>>    struct mmap_cache {
> >>>>>    	char	*mmap_buf;
> >>>>> @@ -985,28 +985,36 @@ struct mmap_cache {
> >>>>>    	off_t   mmap_end_offset;
> >>>>>    };
> >>>>>
> >>>>> +enum {
> >>>>> +	FLAG_UNUSED,
> >>>>> +	FLAG_READY,
> >>>>> +	FLAG_FILLING
> >>>>> +};
> >>>>> +struct page_flag {
> >>>>> +	mdf_pfn_t pfn;
> >>>>> +	char zero;
> >>>>> +	char ready;
> >>>>> +	short index;
> >>>>> +	struct page_flag *next;
> >>>>> +};
> >>>>> +
> >>>>>    struct page_data
> >>>>>    {
> >>>>> -	mdf_pfn_t pfn;
> >>>>> -	int dumpable;
> >>>>> -	int zero;
> >>>>> -	unsigned int flags;
> >>>>> +	pthread_mutex_t mutex;
> >>>>>    	long size;
> >>>>>    	unsigned char *buf;
> >>>>> -	pthread_mutex_t mutex;
> >>>>> -	/*
> >>>>> -	 * whether the page_data is ready to be consumed
> >>>>> -	 */
> >>>>> -	int ready;
> >>>>> +	int flags;
> >>>>> +	int used;
> >>>>>    };
> >>>>>
> >>>>>    struct thread_args {
> >>>>>    	int thread_num;
> >>>>>    	unsigned long len_buf_out;
> >>>>>    	mdf_pfn_t start_pfn, end_pfn;
> >>>>> -	int page_data_num;
> >>>>> +	int page_buf_num;
> >>>>>    	struct cycle *cycle;
> >>>>>    	struct page_data *page_data_buf;
> >>>>> +	struct page_flag *page_flag_buf;
> >>>>>    };
> >>>>>
> >>>>>    /*
> >>>>> @@ -1295,6 +1303,7 @@ struct DumpInfo {
> >>>>>    	pthread_t **threads;
> >>>>>    	struct thread_args *kdump_thread_args;
> >>>>>    	struct page_data *page_data_buf;
> >>>>> +	struct page_flag **page_flag_buf;
> >>>>>    	pthread_rwlock_t usemmap_rwlock;
> >>>>>    	mdf_pfn_t current_pfn;
> >>>>>    	pthread_mutex_t current_pfn_mutex;
> >>>>> --
> >>>>> 1.8.3.1
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> _______________________________________________
> >>>>> kexec mailing list
> >>>>> kexec@lists.infradead.org
> >>>>> http://lists.infradead.org/mailman/listinfo/kexec
> >>>>
> >>>> _______________________________________________
> >>>> kexec mailing list
> >>>> kexec@lists.infradead.org
> >>>> http://lists.infradead.org/mailman/listinfo/kexec
> >>>
> >>>
> >>
> 
> 

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