Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161113AbXB0Jn6 (ORCPT ); Tue, 27 Feb 2007 04:43:58 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161114AbXB0Jn6 (ORCPT ); Tue, 27 Feb 2007 04:43:58 -0500 Received: from rgminet01.oracle.com ([148.87.113.118]:12668 "EHLO rgminet01.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161113AbXB0Jn5 (ORCPT ); Tue, 27 Feb 2007 04:43:57 -0500 Date: Tue, 27 Feb 2007 10:42:11 +0100 From: Jens Axboe To: Suparna Bhattacharya Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Linus Torvalds , Arjan van de Ven , Christoph Hellwig , Andrew Morton , Alan Cox , Ulrich Drepper , Zach Brown , Evgeniy Polyakov , "David S. Miller" , Davide Libenzi , Thomas Gleixner Subject: Re: A quick fio test (was Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3) Message-ID: <20070227094211.GR3822@kernel.dk> References: <20070223125247.GO5737@kernel.dk> <20070223135525.GA31569@in.ibm.com> <20070223145826.GA32465@elte.hu> <20070223151515.GA12960@in.ibm.com> <20070223162508.GA16782@kernel.dk> <20070223171348.GA27838@in.ibm.com> <20070226135736.GF3822@kernel.dk> <20070226141315.GA15631@in.ibm.com> <20070226144548.GH3822@kernel.dk> <20070227043331.GA29942@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070227043331.GA29942@in.ibm.com> X-Brightmail-Tracker: AAAAAQAAAAI= X-Whitelist: TRUE Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4405 Lines: 103 On Tue, Feb 27 2007, Suparna Bhattacharya wrote: > On Mon, Feb 26, 2007 at 03:45:48PM +0100, Jens Axboe wrote: > > On Mon, Feb 26 2007, Suparna Bhattacharya wrote: > > > On Mon, Feb 26, 2007 at 02:57:36PM +0100, Jens Axboe wrote: > > > > > > > > Some more results, using a larger number of processes and io depths. A > > > > repeat of the tests from friday, with added depth 20000 for syslet and > > > > libaio: > > > > > > > > Engine Depth Processes Bw (MiB/sec) > > > > ---------------------------------------------------- > > > > libaio 1 1 602 > > > > syslet 1 1 759 > > > > sync 1 1 776 > > > > libaio 32 1 832 > > > > syslet 32 1 898 > > > > libaio 20000 1 581 > > > > syslet 20000 1 609 > > > > > > > > syslet still on top. Measuring O_DIRECT reads (of 4kb size) on ramfs > > > > with 100 processes each with a depth of 200, reading a per-process > > > > private file of 10mb (need to fit in my ram...) 10 times each. IOW, > > > > doing 10,000MiB of IO in total: > > > > > > But, why ramfs ? Don't we want to exercise the case where O_DIRECT actually > > > blocks ? Or am I missing something here ? > > > > Just overhead numbers for that test case, lets try something like your > > described job. > > > > Test case is doing random reads from /dev/sdb, in chunks of 64kb: > > > > Engine Depth Processes Bw (KiB/sec) > > ---------------------------------------------------- > > libaio 200 100 2813 > > syslet 200 100 3944 > > libaio 20000 1 2793 > > syslet 20000 1 3854 > > sync (*) 20000 1 2866 > > > > deadline was used for IO scheduling, to minimize impact. Not sure why > > syslet actually does so much better here, looing at vmstat the rate is > > steady and all runs are basically 50/50 idle/wait. One difference is > > that the submission itself takes a long time on libaio, since the > > io_submit() will block on request allocation. The generated IO pattern > > from each process is the same for all runs. The drive is a lousy sata > > that doesn't even do queuing, FWIW. > > > I tried the latest fio code with syslet v4, and my results are a little > different - have yet to figure out why or what to make of it. > I hope I have all the right pieces now. > > This is an ext2 filesystem, SCSI AIC7xxx. > > I used an iodepth_batch size of 8 to limit the number of ios in a single > io_submit (thanks for adding that parameter to fio !), like we did in > aio-stress. > > Engine Depth Batch Bw (KiB/sec) > ---------------------------------------------------- > libaio 64 8 17,226 > syslet 64 8 17,620 > libaio 20000 8 18,552 > syslet 20000 8 14,935 > > > Which is not bad, actually. It's not bad for such a high depth/batch setting, but I still wonder why are results are so different. I'll look around for an x86 box with some TCQ/NCQ enabled storage attached for testing. Can you pass me your command line or job file (whatever you use) so we are on the same page? > If I do not specify the iodepth_batch (i.e. default to depth), then the > difference becomes more pronounced at higher depths. However, I doubt > whether anyone would be using such high batch sizes in practice ... > > Engine Depth Batch Bw (KiB/sec) > ---------------------------------------------------- > libaio 64 default 17,429 > syslet 64 default 16,155 > libaio 20000 default 15,494 > syslet 20000 default 7,971 > If iodepth_batch isn't set, the syslet queued io will be serialized and not take advantage of queueing. How does the job file perform with ioengine=sync? > Often times it is the application tuning that makes all the difference, > so am not really sure how much to read into these results. > That's always been the hard part of async io ... Yes I agree, it's handy to get an overview though. -- 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/