From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: How to track down abysmal performance ata - raid1 - crypto - vg/lv - xfs Date: Wed, 4 Aug 2010 07:18:03 -0400 Message-ID: <20100804111803.GA32643@infradead.org> References: <20100804073546.GA7494@comet.dominikbrodowski.net> <20100804085039.GA11671@infradead.org> <20100804091317.GA27779@isilmar-3.linta.de> <20100804092122.GA2998@infradead.org> <20100804073546.GA7494@comet.dominikbrodowski.net> <201008041116.09822@zmi.at> <20100804102526.GB13766@isilmar-3.linta.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20100804102526.GB13766@isilmar-3.linta.de> Sender: linux-raid-owner@vger.kernel.org To: Dominik Brodowski , Michael Monnerie , Christoph Hellwig , linux-raid@vger.kernel.org, xfs@oss.sgi List-Id: linux-raid.ids On Wed, Aug 04, 2010 at 12:25:26PM +0200, Dominik Brodowski wrote: > Hey, > > many thanks for your feedback. It seems the crypto step is the culprit: > > Reading 1.1 GB with dd, iflag=direct, bs=8k: > > /dev/sd* 35.3 MB/s ( 90 %) > /dev/md* 39.1 MB/s (100 %) > /dev/mapper/md*_crypt 3.9 MB/s ( 10 %) > /dev/mapper/vg1-* 3.9 MB/s ( 10 %) > > The "good" news: it also happens on my notebook, even though it has a > different setup (no raid, disk -> lv/vg -> crypt). On my notebook, I'm > more than happy to test out different kernel versions, patches etc. > > /dev/sd* 17.7 MB/s (100 %) > /dev/mapper/vg1-* 16.2 MB/s ( 92 %) > /dev/mapper/*_crypt 3.1 MB/s ( 18 %) The good news is that you have it tracked down, the bad news is that I know very little about dm-crypt. Maybe the issue is the single threaded decryption in dm-crypt? Can you check how much CPU time the dm crypt kernel thread uses?