Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756739Ab0A2ICr (ORCPT ); Fri, 29 Jan 2010 03:02:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754409Ab0A2ICq (ORCPT ); Fri, 29 Jan 2010 03:02:46 -0500 Received: from 0122700014.0.fullrate.dk ([95.166.99.235]:55349 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754169Ab0A2ICp (ORCPT ); Fri, 29 Jan 2010 03:02:45 -0500 Date: Fri, 29 Jan 2010 09:02:44 +0100 From: Jens Axboe To: "Alan D. Brunelle" Cc: "linux-kernel@vger.kernel.org" , whalajam@yahoo.com Subject: Re: Added in stricter no merge semantics for block I/O Message-ID: <20100129080244.GF13771@kernel.dk> References: <1264518884.3278.15.camel@cail> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1264518884.3278.15.camel@cail> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1610 Lines: 37 On Tue, Jan 26 2010, Alan D. Brunelle wrote: > Added in stricter no merge semantics for block I/O > > Updated 'nomerges' tunable to accept a value of '2' - indicating that _no_ > merges at all are to be attempted (not even the simple one-hit cache). > > The following table illustrates the additional benefit - 5 minute runs of > a random I/O load were applied to a dozen devices on a 16-way x86_64 system. > > nomerges Throughput %System Improvement (tput / %sys) > -------- ------------ ----------- ------------------------- > 0 12.45 MB/sec 0.669365609 > 1 12.50 MB/sec 0.641519199 0.40% / 2.71% > 2 12.52 MB/sec 0.639849750 0.56% / 2.96% > > Signed-off-by: Alan D. Brunelle > Cc: jens.axboe@oracle.com > --- > Documentation/ABI/testing/sysfs-block | 14 ++++++++++++++ > Documentation/block/queue-sysfs.txt | 10 +++++----- > block/blk-sysfs.c | 11 +++++++---- > block/elevator.c | 11 ++++++++++- > include/linux/blkdev.h | 3 +++ > 5 files changed, 39 insertions(+), 10 deletions(-) Thanks Alan, I think this is a good addition, I have often before hacked up the "no merges at all" logic for testing purposes as well. I have queued it up for 2.6.34. -- Jens Axboe -- 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/