Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932314AbWHCGlx (ORCPT ); Thu, 3 Aug 2006 02:41:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932320AbWHCGlw (ORCPT ); Thu, 3 Aug 2006 02:41:52 -0400 Received: from mga09.intel.com ([134.134.136.24]:4200 "EHLO orsmga102-1.jf.intel.com") by vger.kernel.org with ESMTP id S932314AbWHCGlv (ORCPT ); Thu, 3 Aug 2006 02:41:51 -0400 X-IronPort-AV: i="4.07,206,1151910000"; d="scan'208"; a="101348622:sNHT10649020613" Date: Wed, 2 Aug 2006 23:36:22 -0700 From: Valerie Henson To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: Akkana Peck , Mark Fasheh , Jesse Barnes , Arjan van de Ven , Chris Wedgwood , jsipek@cs.sunysb.edu, Al Viro , Christoph Hellwig Subject: [RFC] [PATCH] Relative lazy atime Message-ID: <20060803063622.GB8631@goober> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4105 Lines: 116 (Corrected Chris Wedgwood's name and email.) My friend Akkana followed my advice to use noatime on one of her machines, but discovered that mutt was unusable because it always thought that new messages had arrived since the last time it had checked a folder (mbox format). I thought this was a bummer, so I wrote a "relative lazy atime" patch which only updates the atime if the old atime was less than the ctime or mtime. This is not the same as the lazy atime patch of yore[1], which maintained a list of inodes with dirty atimes and wrote them out on unmount. Patch below. Current version (plus test program) is at: http://infohost.nmt.edu/~val/patches.html#lazyatime Thanks to everyone who discussed this with me, especially the folks on #linuxfs on irc.oftc.net. -VAL [1] http://www.ussg.iu.edu/hypermail/linux/kernel/0005.0/0284.html --- Relative lazy atime - only update atime if the old atime was older than the ctime or mtime. We are maintaining atime relative to mtime/ctime. Not for inclusion (yet). Written by Val Henson fs/inode.c | 16 +++++++++++++++- fs/namespace.c | 5 ++++- include/linux/fs.h | 1 + include/linux/mount.h | 1 + 4 files changed, 21 insertions(+), 2 deletions(-) diff -Nrup a/fs/inode.c b/fs/inode.c --- a/fs/inode.c 2006-08-02 23:10:56 -07:00 +++ b/fs/inode.c 2006-08-02 23:10:56 -07:00 @@ -1200,10 +1200,24 @@ void touch_atime(struct vfsmount *mnt, s return; now = current_fs_time(inode->i_sb); - if (!timespec_equal(&inode->i_atime, &now)) { + if (timespec_equal(&inode->i_atime, &now)) + return; + /* + * With lazy atime, only update atime if the previous atime is + * earlier than either the ctime or mtime. + */ + if (!mnt || + !(mnt->mnt_flags & MNT_LAZYATIME) || + (timespec_compare(&inode->i_atime, &inode->i_mtime) < 0) || + (timespec_compare(&inode->i_atime, &inode->i_ctime) < 0)) { inode->i_atime = now; mark_inode_dirty_sync(inode); } + /* + * We could update the in-memory atime here if we wanted, but + * that makes it possible for atime to revert if we evict the + * inode from memory. + */ } EXPORT_SYMBOL(touch_atime); diff -Nrup a/fs/namespace.c b/fs/namespace.c --- a/fs/namespace.c 2006-08-02 23:10:56 -07:00 +++ b/fs/namespace.c 2006-08-02 23:10:56 -07:00 @@ -376,6 +376,7 @@ static int show_vfsmnt(struct seq_file * { MNT_NOEXEC, ",noexec" }, { MNT_NOATIME, ",noatime" }, { MNT_NODIRATIME, ",nodiratime" }, + { MNT_LAZYATIME, ",lazyatime" }, { 0, NULL } }; struct proc_fs_info *fs_infop; @@ -1413,9 +1414,11 @@ long do_mount(char *dev_name, char *dir_ mnt_flags |= MNT_NOATIME; if (flags & MS_NODIRATIME) mnt_flags |= MNT_NODIRATIME; + if (flags & MS_LAZYATIME) + mnt_flags |= MNT_LAZYATIME; flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | - MS_NOATIME | MS_NODIRATIME); + MS_NOATIME | MS_NODIRATIME | MS_LAZYATIME); /* ... and get the mountpoint */ retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd); diff -Nrup a/include/linux/fs.h b/include/linux/fs.h --- a/include/linux/fs.h 2006-08-02 23:10:56 -07:00 +++ b/include/linux/fs.h 2006-08-02 23:10:56 -07:00 @@ -119,6 +119,7 @@ extern int dir_notify_enable; #define MS_PRIVATE (1<<18) /* change to private */ #define MS_SLAVE (1<<19) /* change to slave */ #define MS_SHARED (1<<20) /* change to shared */ +#define MS_LAZYATIME (1<<21) /* Lazily update on-disk access times. */ #define MS_ACTIVE (1<<30) #define MS_NOUSER (1<<31) diff -Nrup a/include/linux/mount.h b/include/linux/mount.h --- a/include/linux/mount.h 2006-08-02 23:10:56 -07:00 +++ b/include/linux/mount.h 2006-08-02 23:10:56 -07:00 @@ -27,6 +27,7 @@ struct namespace; #define MNT_NOEXEC 0x04 #define MNT_NOATIME 0x08 #define MNT_NODIRATIME 0x10 +#define MNT_LAZYATIME 0x20 #define MNT_SHRINKABLE 0x100 - 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/