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

[Jaegeuk Kim <jaegeuk.kim@samsung.com>]

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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

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