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f2fs: optimize fs_lock for better performance 

There is a performance problem: when all sbi->fs_lock are holded, then
all the following threads may get the same next_lock value from sbi->next_lock_num
in function mutex_lock_op, and wait for the same lock(fs_lock[next_lock]),
it may cause performance reduce.
So we move the sbi->next_lock_num++ before getting lock, this will average the
following threads if all sbi->fs_lock are holded.

v1-->v2:
	Drop the needless spin_lock as Jaegeuk suggested.

Suggested-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
Signed-off-by: Yu Chao <chao2.yu@samsung.com>
Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
This commit is contained in:
Yu Chao 2013-09-12 11:17:51 +08:00 committed by Jaegeuk Kim
parent 4a10c2ac2f
commit e76eebee70
1 changed files with 2 additions and 2 deletions
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4
fs/f2fs/f2fs.h
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@ -544,15 +544,15 @@ static inline void mutex_unlock_all(struct f2fs_sb_info *sbi)
static inline int mutex_lock_op(struct f2fs_sb_info *sbi)
{
unsigned char next_lock = sbi->next_lock_num % NR_GLOBAL_LOCKS;
unsigned char next_lock;
int i = 0;
for (; i < NR_GLOBAL_LOCKS; i++)
if (mutex_trylock(&sbi->fs_lock[i]))
return i;
next_lock = sbi->next_lock_num++ % NR_GLOBAL_LOCKS;
mutex_lock(&sbi->fs_lock[next_lock]);
sbi->next_lock_num++;
return next_lock;
}