From b12536c27043f1c21195e587eb59950428326e22 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Fri, 18 Sep 2009 13:05:47 -0700 Subject: [PATCH] vfs: optimization for touch_atime() Some benchmark testing shows touch_atime to be high up in profile logs for IO intensive workloads. Most likely that's due to the lock in mnt_want_write(). Unfortunately touch_atime first takes the lock, and then does all the other tests that could avoid atime updates (like noatime or relatime). Do it the other way round -- first try to avoid the update and only then if that didn't succeed take the lock. That works because none of the atime avoidance tests rely on locking. This also eliminates a goto. Signed-off-by: Andi Kleen Cc: Christoph Hellwig Reviewed-by: Valerie Aurora Cc: Al Viro Cc: Dave Hansen Signed-off-by: Andrew Morton Signed-off-by: Al Viro --- fs/inode.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/fs/inode.c b/fs/inode.c index fa506d539653..31168fd45bdc 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -1416,31 +1416,31 @@ void touch_atime(struct vfsmount *mnt, struct dentry *dentry) struct inode *inode = dentry->d_inode; struct timespec now; - if (mnt_want_write(mnt)) - return; if (inode->i_flags & S_NOATIME) - goto out; + return; if (IS_NOATIME(inode)) - goto out; + return; if ((inode->i_sb->s_flags & MS_NODIRATIME) && S_ISDIR(inode->i_mode)) - goto out; + return; if (mnt->mnt_flags & MNT_NOATIME) - goto out; + return; if ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode)) - goto out; + return; now = current_fs_time(inode->i_sb); if (!relatime_need_update(mnt, inode, now)) - goto out; + return; if (timespec_equal(&inode->i_atime, &now)) - goto out; + return; + + if (mnt_want_write(mnt)) + return; inode->i_atime = now; mark_inode_dirty_sync(inode); -out: mnt_drop_write(mnt); } EXPORT_SYMBOL(touch_atime);