From: Jan Kara Subject: Re: [PATCH] ext4: turn on i_version updates by default Date: Tue, 15 May 2012 12:30:21 +0200 Message-ID: <20120515103021.GD22359@quack.suse.cz> References: <20120514140618.GA29902@fieldses.org> <9124E59E-2479-4C32-A528-3237B48DEC01@dilger.ca> <1337036918.2522.32.camel@lade.trondhjem.org> <20120514235432.GA3199@fieldses.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andreas Dilger , "Myklebust, Trond" , Theodore Ts'o , "linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" To: "J. Bruce Fields" Return-path: Content-Disposition: inline In-Reply-To: <20120514235432.GA3199-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org> Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-ext4.vger.kernel.org On Mon 14-05-12 19:54:32, J. Bruce Fields wrote: > On Mon, May 14, 2012 at 05:33:04PM -0600, Andreas Dilger wrote: > > I said as much in another reply - that once i_version is used on > > a filesystem, it should be made "sticky" (i.e. permanently enabled > > for that filesystem). However, until that time it shouldn't be > > enabled just because it might one day be used. > > > > Even better than just blindly bumping the i_version on every change, > > it would be better to have users of i_version (i.e. knfsd) flag the > > inode with "needs i_version update" then read the version. When the > > filesystem/VFS bumps i_version the next time it can clear this flag > > and not update i_version again until after the next time i_version > > is actually used. > > I really don't want to do anything more complicated than necessary. > > What would be the worst-case test for the extra inode dirtying, so we > can see what the numbers actually are? Something like: int fd, i; struct timeval tv[2]; fd = open("file", O_CREAT | O_RDWR, 0644); if (fd < 0) return 1; for (i = 0; i < 1000000; i++) { gettimeofday(tv); tv[1] = tv[0]; if (futimes(fd, tv) < 0) return 1; } return 0; And see how long does it take with and without i_version? Honza -- Jan Kara SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html