Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754907AbbHJRXv (ORCPT ); Mon, 10 Aug 2015 13:23:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53028 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753931AbbHJRXu (ORCPT ); Mon, 10 Aug 2015 13:23:50 -0400 From: Jeff Moyer To: Christoph Hellwig Cc: Jens Axboe , linux-kernel@vger.kernel.org, dmilburn@redhat.com Subject: Re: [patch] Revert "block: remove artifical max_hw_sectors cap" References: <20150721130246.GA28676@infradead.org> <20150730135134.GA14734@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: Mon, 10 Aug 2015 13:23:48 -0400 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1407 Lines: 34 Christoph Hellwig writes: > Hi Jeff, > > thanks for the detailed numbers! > > The bigger I/O size makes a drastic impact for Linux software RAID > setups, for which this was a driver. For the RAID5/6 over SATA disks > setups that I was benchmarking this it gives between 20 and 40% better > sequential read and write numbers. Hi, Christoph, Unfortunately, I'm unable to reproduce your results (though my test setup uses SAS disks, not SATA). I tried with a 10 data disk md RAID5, with 32k and 128k chunk sizes. I modified the fio program to read/write multiples of the stripe width, and I also used aio-stress over a range of queue depth and I/O sizes for read, write, random read and random write. I didn't see any measurable performance difference. Do you still have access to your test setup? What do you think about reinstituting the artificial max_sectors_kb cap, but bumping the default up from 512KB to 1280KB? I had our performance team run numbers on their test setup (which is a 12 disk raid0 with 32k chunk size, fwiw) with max_sectors_kb set to 1280 and, aside from one odd data point, things looked good. 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/