From: Andi Kleen <andi@xxxxxxxxxxxxxx> 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 <ak@xxxxxxxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> Reviewed-by: Valerie Aurora <vaurora@xxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Dave Hansen <haveblue@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/inode.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff -puN fs/inode.c~vfs-optimization-for-touch_atime fs/inode.c --- a/fs/inode.c~vfs-optimization-for-touch_atime +++ a/fs/inode.c @@ -1411,31 +1411,31 @@ void touch_atime(struct vfsmount *mnt, s 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); _ -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
