From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753197AbbG3Nvh (ORCPT ); Thu, 30 Jul 2015 09:51:37 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:58454 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752493AbbG3Nvg (ORCPT ); Thu, 30 Jul 2015 09:51:36 -0400 Date: Thu, 30 Jul 2015 06:51:34 -0700 From: Christoph Hellwig To: Jeff Moyer Cc: Jens Axboe , linux-kernel@vger.kernel.org, dmilburn@redhat.com Subject: Re: [patch] Revert "block: remove artifical max_hw_sectors cap" Message-ID: <20150730135134.GA14734@infradead.org> References: <20150721130246.GA28676@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Besides those I've tested it on various SSDs where it didn't make any difference, e.g. on the laptop with a Samsung 840 Evo I'm currently travelling with and your fio script. First line max_sectors_kb = 512, second line max_sectors_kb = max_hw_sectors_kb (32767) Run status group 0 (all jobs): WRITE: io=1024.0MB, aggrb=471270KB/s, minb=471270KB/s, maxb=471270KB/s, mint=2225msec, maxt=2225msec WRITE: io=1024.0MB, aggrb=475976KB/s, minb=475976KB/s, maxb=475976KB/s, mint=2203msec, maxt=2203msec Run status group 1 (all jobs): WRITE: io=1024.0MB, aggrb=477276KB/s, minb=477276KB/s, maxb=477276KB/s, mint=2197msec, maxt=2197msec WRITE: io=1024.0MB, aggrb=479677KB/s, minb=479677KB/s, maxb=479677KB/s, mint=2186msec, maxt=2186msec Run status group 2 (all jobs): WRITE: io=1024.0MB, aggrb=488618KB/s, minb=488618KB/s, maxb=488618KB/s, mint=2146msec, maxt=2146msec WRITE: io=1024.0MB, aggrb=489302KB/s, minb=489302KB/s, maxb=489302KB/s, mint=2143msec, maxt=2143msec