Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754704AbZGFTY5 (ORCPT ); Mon, 6 Jul 2009 15:24:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754099AbZGFTYr (ORCPT ); Mon, 6 Jul 2009 15:24:47 -0400 Received: from one.firstfloor.org ([213.235.205.2]:38299 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753922AbZGFTYq (ORCPT ); Mon, 6 Jul 2009 15:24:46 -0400 From: Andi Kleen Message-Id: <20090706924.495556466@firstfloor.org> To: viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH] [1/2] Optimization for touch_atime Date: Mon, 6 Jul 2009 21:24:46 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1936 Lines: 70 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 --- fs/inode.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) Index: linux-2.6.30-ak/fs/inode.c =================================================================== --- linux-2.6.30-ak.orig/fs/inode.c +++ linux-2.6.30-ak/fs/inode.c @@ -1361,31 +1361,31 @@ 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-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/