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authorZhang, Yanmin <yanmin_zhang@linux.intel.com>2009-07-05 12:08:08 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-07-06 13:57:03 -0700
commit3beab0b42413e83a7907db7176b54c840fc75a81 (patch)
tree385c4e725fb56c0416be1512b50c357e9bc50b6b /fs
parentf386c61fe1a1f36f0e434f1b577e6b112698caf7 (diff)
sys_sync(): fix 16% performance regression in ffsb create_4k test
I run many ffsb test cases on JBODs (typically 13/12 disks). Comparing with kernel 2.6.30, 2.6.31-rc1 has about 16% regression with ffsb_create_4k. The sub test case creates files continuously for 10 minitues and every file is 1MB. Bisect located below patch. 5cee5815d1564bbbd505fea86f4550f1efdb5cd0 is first bad commit commit 5cee5815d1564bbbd505fea86f4550f1efdb5cd0 Author: Jan Kara <jack@suse.cz> Date: Mon Apr 27 16:43:51 2009 +0200 vfs: Make sys_sync() use fsync_super() (version 4) It is unnecessarily fragile to have two places (fsync_super() and do_sync()) doing data integrity sync of the filesystem. Alter __fsync_super() to accommodate needs of both callers and use it. So after this patch __fsync_super() is the only place where we gather all the calls needed to properly send all data on a filesystem to disk. As a matter of fact, ffsb calls sys_sync in the end to make sure all data is flushed to disks and the flushing is counted into the result. vmstat shows ffsb is blocked when syncing for a long time. With 2.6.30, ffsb is blocked for a short time. I checked the patch and did experiments to recover the original methods. Eventually, the root cause is the patch deletes the calling to wakeup_pdflush when syncing, so only ffsb is blocked on disk I/O. wakeup_pdflush could ask pdflush to write back pages with ffsb at the same time. [akpm@linux-foundation.org: restore comment too] Signed-off-by: Zhang Yanmin <yanmin_zhang@linux.intel.com> Cc: Jan Kara <jack@suse.cz> Cc: Al Viro <viro@zeniv.linux.org.uk> Acked-by: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/sync.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/fs/sync.c b/fs/sync.c
index dd200025af8..3422ba61d86 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -112,8 +112,13 @@ restart:
mutex_unlock(&mutex);
}
+/*
+ * sync everything. Start out by waking pdflush, because that writes back
+ * all queues in parallel.
+ */
SYSCALL_DEFINE0(sync)
{
+ wakeup_pdflush(0);
sync_filesystems(0);
sync_filesystems(1);
if (unlikely(laptop_mode))