Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753226Ab0FWNEi (ORCPT ); Wed, 23 Jun 2010 09:04:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58996 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753017Ab0FWNEJ (ORCPT ); Wed, 23 Jun 2010 09:04:09 -0400 From: Jeff Moyer To: Christoph Hellwig Cc: axboe@kernel.dk, vgoyal@redhat.com, linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org Subject: Re: [PATCH 0/3 v5][RFC] ext3/4: enhance fsync performance when using CFQ References: <1277242502-9047-1-git-send-email-jmoyer@redhat.com> <20100623092028.GA13900@infradead.org> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Wed, 23 Jun 2010 09:03:52 -0400 In-Reply-To: <20100623092028.GA13900@infradead.org> (Christoph Hellwig's message of "Wed, 23 Jun 2010 05:20:28 -0400") Message-ID: User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1802 Lines: 40 Christoph Hellwig writes: > On Tue, Jun 22, 2010 at 05:34:59PM -0400, Jeff Moyer wrote: >> Hi, >> >> Running iozone with the fsync flag, or fs_mark, the performance of CFQ is >> far worse than that of deadline for enterprise class storage when dealing >> with file sizes of 8MB or less. I used the following command line as a >> representative test case: >> >> fs_mark -S 1 -D 10000 -N 100000 -d /mnt/test/fs_mark -s 65536 -t 1 -w 4096 -F >> >> When run using the deadline I/O scheduler, an average of the first 5 numbers >> will give you 448.4 files / second. CFQ will yield only 106.7. With >> this patch series applied (and the two patches I sent yesterday), CFQ now >> achieves 462.5 files / second. >> >> This patch set is still an RFC. I'd like to make it perform better when >> there is a competing sequential reader present. For now, I've addressed >> the concerns voiced about the previous posting. > > What happened to the initial idea of just using the BIO_RW_META flag > for log writes? In the end log writes are the most important writes you > have in a journaled filesystem, and they should not be effect to any > kind of queue idling logic or other interruption. Log I/O is usually > very little (unless you use old XFS code with a worst-case directory > manipulation workload), and very latency sensitive. Vivek showed that starting firefox in the presence of a processing doing fsyncs (using the RQ_META approach) took twice as long as without the patch: http://lkml.org/lkml/2010/4/6/276 Cheers, Jeff -- 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/