[PATCH] f2fs: avoid frequent background GC

[PATCH] f2fs: avoid frequent background GC

[Jaegeuk Kim]

If there is no victim segments selected by background GC, let's wait
a little bit longer time to collect dirty segments.
By default, let's give 10 minutes.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
---
 fs/f2fs/gc.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
index 30b2db0..1190d57 100644
--- a/fs/f2fs/gc.h
+++ b/fs/f2fs/gc.h
@@ -13,9 +13,9 @@
 						 * whether IO subsystem is idle
 						 * or not
 						 */
-#define GC_THREAD_MIN_SLEEP_TIME	10000 /* milliseconds */
+#define GC_THREAD_MIN_SLEEP_TIME	10000	/* milliseconds */
 #define GC_THREAD_MAX_SLEEP_TIME	30000
-#define GC_THREAD_NOGC_SLEEP_TIME	10000
+#define GC_THREAD_NOGC_SLEEP_TIME	600000	/* wait 10 min */
 #define LIMIT_INVALID_BLOCK	40 /* percentage over total user space */
 #define LIMIT_FREE_BLOCK	40 /* percentage over invalid + free space */
 
-- 
1.8.1.3.566.gaa39828

Re: [PATCH] f2fs: avoid frequent background GC

[Namjae Jeon]

Hi Jaegeuk,

With the change in the value of GC_THREAD_NOGC_SLEEP_TIME to 600000,
we will need to rewrite the gc_thread_func().
As there will be several paths which will not be reached or will have
no meaning after this change.

Considering the cases:
/* if return value is not zero, no victim was selected */
                if (f2fs_gc(sbi))
                        wait_ms = GC_THREAD_NOGC_SLEEP_TIME;
                else if (wait_ms == GC_THREAD_NOGC_SLEEP_TIME)
                        wait_ms = GC_THREAD_MAX_SLEEP_TIME;

Before this point, there are ‘2’ functions to change ‘wait_ms” ->
increase_sleep_time and decrease_sleep_time.
When we consider increase_sleep_time()  - the maximum possible value
for ‘wait_ms’ after coming out of this can be:
GC_THREAD_MAX_SLEEP_TIME
And in case in the last iteration it was set to
GC_THREAD_NOGC_SLEEP_TIME, once it enters increase_sleep_time() - the
value will be reseted to maximum GC_THREAD_MAX_SLEEP_TIME.
So,
                else if (wait_ms == GC_THREAD_NOGC_SLEEP_TIME)
                        wait_ms = GC_THREAD_MAX_SLEEP_TIME;
becomes unreachable path.

And second, maybe, After setting to GC_THREAD_NOGC_SLEEP_TIME(10min),
Although there are invalid blocks, GC thread might be sleep 9min
50sec.
Let me know your opinion.

Thanks.

2013/4/25, Jaegeuk Kim <jaegeuk.kim@samsung.com>:
> If there is no victim segments selected by background GC, let's wait
> a little bit longer time to collect dirty segments.
> By default, let's give 10 minutes.
>
> Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
> ---
>  fs/f2fs/gc.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
> index 30b2db0..1190d57 100644
> --- a/fs/f2fs/gc.h
> +++ b/fs/f2fs/gc.h
> @@ -13,9 +13,9 @@
>  						 * whether IO subsystem is idle
>  						 * or not
>  						 */
> -#define GC_THREAD_MIN_SLEEP_TIME	10000 /* milliseconds */
> +#define GC_THREAD_MIN_SLEEP_TIME	10000	/* milliseconds */
>  #define GC_THREAD_MAX_SLEEP_TIME	30000
> -#define GC_THREAD_NOGC_SLEEP_TIME	10000
> +#define GC_THREAD_NOGC_SLEEP_TIME	600000	/* wait 10 min */
>  #define LIMIT_INVALID_BLOCK	40 /* percentage over total user space */
>  #define LIMIT_FREE_BLOCK	40 /* percentage over invalid + free space */
>
> --
> 1.8.1.3.566.gaa39828
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Re: [PATCH v2] f2fs: avoid frequent background GC

[Jaegeuk Kim]

[-- Attachment #1: Type: text/plain, Size: 2663 bytes --]

Hi, Namjae,

Agreed. How about this?

Chang log from v1:
 o change timings - min 30s, max 60s, nogc 5 min
 o remove nonreachable routine
 o consider NOGC_SLEEP_TIME in increate/decrease_sleep_time

From 806e344624414fcf9fc87f6193265859027d51b5 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk.kim@samsung.com>
Date: Wed, 24 Apr 2013 13:00:14 +0900
Subject: [PATCH] f2fs: avoid frequent background GC
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net

If there is no victim segments selected by background GC, let's wait
a little bit longer time to collect dirty segments.
By default, let's give 5 minutes.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
---
 fs/f2fs/gc.c |  3 ---
 fs/f2fs/gc.h | 12 +++++++++---
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 1ca3324..6ed3263 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -82,9 +82,6 @@ static int gc_thread_func(void *data)
 		/* if return value is not zero, no victim was selected */
 		if (f2fs_gc(sbi))
 			wait_ms = GC_THREAD_NOGC_SLEEP_TIME;
-		else if (wait_ms == GC_THREAD_NOGC_SLEEP_TIME)
-			wait_ms = GC_THREAD_MAX_SLEEP_TIME;
-
 	} while (!kthread_should_stop());
 	return 0;
 }
diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
index 30b2db0..2c6a6bd 100644
--- a/fs/f2fs/gc.h
+++ b/fs/f2fs/gc.h
@@ -13,9 +13,9 @@
 						 * whether IO subsystem is idle
 						 * or not
 						 */
-#define GC_THREAD_MIN_SLEEP_TIME	10000 /* milliseconds */
-#define GC_THREAD_MAX_SLEEP_TIME	30000
-#define GC_THREAD_NOGC_SLEEP_TIME	10000
+#define GC_THREAD_MIN_SLEEP_TIME	30000	/* milliseconds */
+#define GC_THREAD_MAX_SLEEP_TIME	60000
+#define GC_THREAD_NOGC_SLEEP_TIME	300000	/* wait 5 min */
 #define LIMIT_INVALID_BLOCK	40 /* percentage over total user space */
 #define LIMIT_FREE_BLOCK	40 /* percentage over invalid + free space */
 
@@ -58,6 +58,9 @@ static inline block_t limit_free_user_blocks(struct
f2fs_sb_info *sbi)
 
 static inline long increase_sleep_time(long wait)
 {
+	if (wait == GC_THREAD_NOGC_SLEEP_TIME)
+		return wait;
+
 	wait += GC_THREAD_MIN_SLEEP_TIME;
 	if (wait > GC_THREAD_MAX_SLEEP_TIME)
 		wait = GC_THREAD_MAX_SLEEP_TIME;
@@ -66,6 +69,9 @@ static inline long increase_sleep_time(long wait)
 
 static inline long decrease_sleep_time(long wait)
 {
+	if (wait == GC_THREAD_NOGC_SLEEP_TIME)
+		wait = GC_THREAD_MAX_SLEEP_TIME;
+
 	wait -= GC_THREAD_MIN_SLEEP_TIME;
 	if (wait <= GC_THREAD_MIN_SLEEP_TIME)
 		wait = GC_THREAD_MIN_SLEEP_TIME;
-- 
1.8.1.3.566.gaa39828



-- 
Jaegeuk Kim
Samsung

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 836 bytes --]

Re: [PATCH v2] f2fs: avoid frequent background GC

[Namjae Jeon]

2013/4/25, Jaegeuk Kim <jaegeuk.kim@samsung.com>:
> Hi, Namjae,
>
> Agreed. How about this?
>
> Chang log from v1:
>  o change timings - min 30s, max 60s, nogc 5 min
>  o remove nonreachable routine
>  o consider NOGC_SLEEP_TIME in increate/decrease_sleep_time
>
> From 806e344624414fcf9fc87f6193265859027d51b5 Mon Sep 17 00:00:00 2001
> From: Jaegeuk Kim <jaegeuk.kim@samsung.com>
> Date: Wed, 24 Apr 2013 13:00:14 +0900
> Subject: [PATCH] f2fs: avoid frequent background GC
> Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
> linux-f2fs-devel@lists.sourceforge.net
>
> If there is no victim segments selected by background GC, let's wait
> a little bit longer time to collect dirty segments.
> By default, let's give 5 minutes.
>
> Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
Looks good!
Reviewed-by: Namjae Jeon <namjae.jeon@samsung.com>

Thanks~