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

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

[Zhou Wenjian]

The origin implementation of --num-threads wastes a lot of time
dealing with the filtered pages. So it has a great performance degradation
when -d 31 is specified.
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.
It won't waste time and memory for filtered page. So it has a good behaviour in -d 31.

Some tests results:

      -l                                   -c
-d 31: 2.6                                 11.3 (without num-threads)
       num-threads    origin    new        origin    new
       1              13.2      2.9        22.4      13.2
       2              11.6      2.46       15.3      7.3
       4              10.4      3.2        12.3      5.7
-d 0:  32.7                                151.2(without num-threads)
       1              43.3      45.3       158.9     159.4
       2              21.2      23.0       81.8      83.2
       4              18.2      21.4       46.1      47.5

These tests are executed in the second kernel with /proc/vmcore.
---
 makedumpfile.c | 266 +++++++++++++++++++++++++++++++++++++++------------------
 makedumpfile.h |  26 +++---
 2 files changed, 196 insertions(+), 96 deletions(-)

diff --git a/makedumpfile.c b/makedumpfile.c
index fa0b779..8cf274b 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 +7172,48 @@ 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)
-				continue;
-
-			if (page_data_buf[index].ready != 0)
+			/* 1 means page_flag_buf is ready to be used */
+			if (page_flag_buf->ready == 1)
 				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++;
+			/* 2 means page_flag_buf is being filled */
+			page_flag_buf->ready = 2;
+			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 = 1;
+				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 +7226,11 @@ 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 +7280,16 @@ 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 = 1;
+			page_flag_buf = page_flag_buf->next;
 
 		}
-	}
 
+		pthread_mutex_unlock(&page_data_buf[index].mutex);
+	}
 	retval = NULL;
 
 fail:
@@ -7265,14 +7317,15 @@ 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 +7372,11 @@ 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 +7390,9 @@ 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 +7405,101 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
 		}
 	}
 
-	consuming_pfn = start_pfn;
-	index = -1;
+	while (1) {
+		consuming = 0;
+		check_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;
+			end_count = 0;
 
-	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++) {
 
-		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;
-		}
+				/*
+				 * ready == 0 means the page_flag_buf haven't been used.
+				 * So we will skip it.
+				 */
+				if (info->page_flag_buf[i]->ready == 0)
+					continue;
+				temp_pfn = info->page_flag_buf[i]->pfn;
 
-		/*
-		 * check pfn first without mutex locked to reduce the time
-		 * trying to lock the mutex
-		 */
-		if (page_data_buf[index].pfn != consuming_pfn)
-			continue;
+				/*
+				 * count how many threads have reached the end.
+				 */ 
+				if (temp_pfn >= end_pfn) {
+					end_count++;
+					continue;
+				}
 
-		if (pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
-			continue;
+				if (current_pfn < temp_pfn)
+					continue;
 
-		/* 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;
+				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 != 1) {
+				gettimeofday(&new, NULL);
+				if (new.tv_sec - last.tv_sec > WAIT_TIME) {
+					ERRMSG("Can't get data of pfn.\n");
+					goto out;
+				}
+			}
+
+			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 +7515,12 @@ 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 = 0;
+		info->page_flag_buf[consuming] = info->page_flag_buf[consuming]->next;
 	}
-
+finish:
 	ret = TRUE;
 	/*
 	 * print [100 %]
@@ -7464,7 +7559,7 @@ 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 +7659,7 @@ 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..7452e24 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 +985,31 @@ struct mmap_cache {
 	off_t   mmap_end_offset;
 };
 
+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 +1298,7 @@ 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 RFC] Improve the performance of --num-threads -d 31

["Zhou, Wenjian/周文剑"]

Hello,

Several weeks ago, we talked about the performance degradation of --num-threads 1.
I found in the origin implementation, handling filtered page and zero page spends more
time than without num-threads.
I think that's why --num-threads 1 is so different from --num-threads 0.

I rewrite the logic in this patch. And the new implementation can resolve the degradation
of -d 31. It can reduce the time of handling filtered page.
But it seems not effective for handling zero page.

-- 
Thanks
Zhou

On 01/18/2016 10:00 AM, Zhou Wenjian wrote:
> The origin implementation of --num-threads wastes a lot of time
> dealing with the filtered pages. So it has a great performance degradation
> when -d 31 is specified.
> 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.
> It won't waste time and memory for filtered page. So it has a good behaviour in -d 31.
>
> Some tests results:
>
>        -l                                   -c
> -d 31: 2.6                                 11.3 (without num-threads)
>         num-threads    origin    new        origin    new
>         1              13.2      2.9        22.4      13.2
>         2              11.6      2.46       15.3      7.3
>         4              10.4      3.2        12.3      5.7
> -d 0:  32.7                                151.2(without num-threads)
>         1              43.3      45.3       158.9     159.4
>         2              21.2      23.0       81.8      83.2
>         4              18.2      21.4       46.1      47.5
>
> These tests are executed in the second kernel with /proc/vmcore.
> ---
>   makedumpfile.c | 266 +++++++++++++++++++++++++++++++++++++++------------------
>   makedumpfile.h |  26 +++---
>   2 files changed, 196 insertions(+), 96 deletions(-)
>
> diff --git a/makedumpfile.c b/makedumpfile.c
> index fa0b779..8cf274b 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 +7172,48 @@ 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)
> -				continue;
> -
> -			if (page_data_buf[index].ready != 0)
> +			/* 1 means page_flag_buf is ready to be used */
> +			if (page_flag_buf->ready == 1)
>   				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++;
> +			/* 2 means page_flag_buf is being filled */
> +			page_flag_buf->ready = 2;
> +			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 = 1;
> +				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 +7226,11 @@ 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 +7280,16 @@ 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 = 1;
> +			page_flag_buf = page_flag_buf->next;
>
>   		}
> -	}
>
> +		pthread_mutex_unlock(&page_data_buf[index].mutex);
> +	}
>   	retval = NULL;
>
>   fail:
> @@ -7265,14 +7317,15 @@ 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 +7372,11 @@ 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 +7390,9 @@ 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 +7405,101 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>   		}
>   	}
>
> -	consuming_pfn = start_pfn;
> -	index = -1;
> +	while (1) {
> +		consuming = 0;
> +		check_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;
> +			end_count = 0;
>
> -	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++) {
>
> -		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;
> -		}
> +				/*
> +				 * ready == 0 means the page_flag_buf haven't been used.
> +				 * So we will skip it.
> +				 */
> +				if (info->page_flag_buf[i]->ready == 0)
> +					continue;
> +				temp_pfn = info->page_flag_buf[i]->pfn;
>
> -		/*
> -		 * check pfn first without mutex locked to reduce the time
> -		 * trying to lock the mutex
> -		 */
> -		if (page_data_buf[index].pfn != consuming_pfn)
> -			continue;
> +				/*
> +				 * count how many threads have reached the end.
> +				 */
> +				if (temp_pfn >= end_pfn) {
> +					end_count++;
> +					continue;
> +				}
>
> -		if (pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
> -			continue;
> +				if (current_pfn < temp_pfn)
> +					continue;
>
> -		/* 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;
> +				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 != 1) {
> +				gettimeofday(&new, NULL);
> +				if (new.tv_sec - last.tv_sec > WAIT_TIME) {
> +					ERRMSG("Can't get data of pfn.\n");
> +					goto out;
> +				}
> +			}
> +
> +			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 +7515,12 @@ 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 = 0;
> +		info->page_flag_buf[consuming] = info->page_flag_buf[consuming]->next;
>   	}
> -
> +finish:
>   	ret = TRUE;
>   	/*
>   	 * print [100 %]
> @@ -7464,7 +7559,7 @@ 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 +7659,7 @@ 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..7452e24 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 +985,31 @@ struct mmap_cache {
>   	off_t   mmap_end_offset;
>   };
>
> +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 +1298,7 @@ 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;
>



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RE: [PATCH RFC] Improve the performance of --num-threads -d 31

[Atsushi Kumagai]

Hello Zhou,

>The origin implementation of --num-threads wastes a lot of time
>dealing with the filtered pages. So it has a great performance degradation
>when -d 31 is specified.
>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.
>It won't waste time and memory for filtered page. So it has a good behaviour in -d 31.
>
>Some tests results:
>
>      -l                                   -c
>-d 31: 2.6                                 11.3 (without num-threads)
>       num-threads    origin    new        origin    new
>       1              13.2      2.9        22.4      13.2
>       2              11.6      2.46       15.3      7.3
>       4              10.4      3.2        12.3      5.7
>-d 0:  32.7                                151.2(without num-threads)
>       1              43.3      45.3       158.9     159.4
>       2              21.2      23.0       81.8      83.2
>       4              18.2      21.4       46.1      47.5
>
>These tests are executed in the second kernel with /proc/vmcore.

I appreciate your work, the effect looks great.
There are still some performance degradation depending on the dump level,
but the problem we discussed is "especially -d31 is too slow",
so I think this patch is enough for now.

BTW, I have some small comments for cleanup, please check below.

>---
> makedumpfile.c | 266 +++++++++++++++++++++++++++++++++++++++------------------
> makedumpfile.h |  26 +++---
> 2 files changed, 196 insertions(+), 96 deletions(-)
>
>diff --git a/makedumpfile.c b/makedumpfile.c
>index fa0b779..8cf274b 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 +7172,48 @@ 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)
>-				continue;
>-
>-			if (page_data_buf[index].ready != 0)
>+			/* 1 means page_flag_buf is ready to be used */
>+			if (page_flag_buf->ready == 1)
> 				continue;

For status flag, enum is preferable to explaining a magic number by comment.

>
>-			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++;
>+			/* 2 means page_flag_buf is being filled */
>+			page_flag_buf->ready = 2;
>+			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 = 1;
>+				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 +7226,11 @@ 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 +7280,16 @@ 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 = 1;
>+			page_flag_buf = page_flag_buf->next;
>
> 		}
>-	}
>
>+		pthread_mutex_unlock(&page_data_buf[index].mutex);
>+	}
> 	retval = NULL;
>
> fail:
>@@ -7265,14 +7317,15 @@ 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 +7372,11 @@ 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 +7390,9 @@ 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 +7405,101 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> 		}
> 	}
>
>-	consuming_pfn = start_pfn;
>-	index = -1;
>+	while (1) {
>+		consuming = 0;
>+		check_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.
>+		 */
>+		/*
>+		 *
>+		 */

I hope such garbage will be removed in the next version.

Thanks,
Atsushi Kumagai

>+		while (1) {
>+			current_pfn = end_pfn;
>+			end_count = 0;
>
>-	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++) {
>
>-		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;
>-		}
>+				/*
>+				 * ready == 0 means the page_flag_buf haven't been used.
>+				 * So we will skip it.
>+				 */
>+				if (info->page_flag_buf[i]->ready == 0)
>+					continue;
>+				temp_pfn = info->page_flag_buf[i]->pfn;
>
>-		/*
>-		 * check pfn first without mutex locked to reduce the time
>-		 * trying to lock the mutex
>-		 */
>-		if (page_data_buf[index].pfn != consuming_pfn)
>-			continue;
>+				/*
>+				 * count how many threads have reached the end.
>+				 */
>+				if (temp_pfn >= end_pfn) {
>+					end_count++;
>+					continue;
>+				}
>
>-		if (pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
>-			continue;
>+				if (current_pfn < temp_pfn)
>+					continue;
>
>-		/* 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;
>+				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 != 1) {
>+				gettimeofday(&new, NULL);
>+				if (new.tv_sec - last.tv_sec > WAIT_TIME) {
>+					ERRMSG("Can't get data of pfn.\n");
>+					goto out;
>+				}
>+			}
>+
>+			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 +7515,12 @@ 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 = 0;
>+		info->page_flag_buf[consuming] = info->page_flag_buf[consuming]->next;
>
> 	}
>-
>+finish:
> 	ret = TRUE;
> 	/*
> 	 * print [100 %]
>@@ -7464,7 +7559,7 @@ 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 +7659,7 @@ 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..7452e24 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 +985,31 @@ struct mmap_cache {
> 	off_t   mmap_end_offset;
> };
>
>+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 +1298,7 @@ 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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