From: Larry McVoy Subject: Re: [Jfs-discussion] benchmark results Date: Fri, 25 Dec 2009 08:22:38 -0800 Message-ID: <20091225162238.GB19303@bitmover.com> References: <19251.26403.762180.228181@tree.ty.sabi.co.uk> <20091224212756.GM21594@thunk.org> <20091225161453.GD32757@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: jfs-discussion@lists.sourceforge.net, linux-nilfs@vger.kernel.org, linux-ext4@vger.kernel.org, Peter Grandi , reiserfs-devel@vger.kernel.org, ext-users , xfs@oss.sgi.com, linux-btrfs@vger.kernel.org To: tytso@mit.edu Return-path: Content-Disposition: inline In-Reply-To: <20091225161453.GD32757@thunk.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com List-Id: linux-ext4.vger.kernel.org On Fri, Dec 25, 2009 at 11:14:53AM -0500, tytso@mit.edu wrote: > On Thu, Dec 24, 2009 at 05:52:34PM -0800, Christian Kujau wrote: > > > > Well, I do "sync" after each operation, so the data should be on disk, but > > that doesn't mean it'll clear the filesystem buffers - but this doesn't > > happen that often in the real world too. Also, all filesystem were tested > > equally (I hope), yet some filesystem perform better than another - even > > if all the content copied/tar'ed/removed would perfectly well fit into the > > machines RAM. > > Did you include the "sync" in part of what you timed? Peter was quite > right --- the fact that the measured bandwidth in your "cp" test is > five times faster than the disk bandwidth as measured by hdparm, and > many file systems had exactly the same bandwidth, makes me very > suspicious that what was being measured was primarily memory bandwidth > --- and not very useful when trying to measure file system > performance. Dudes, sync() doesn't flush the fs cache, you have to unmount for that. Once upon a time Linux had an ioctl() to flush the fs buffers, I used it in lmbench. ioctl(fd, BLKFLSBUF, 0); No idea if that is still supported, but sync() is a joke for benchmarking. -- --- Larry McVoy lm at bitmover.com http://www.bitkeeper.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs