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Open Source and information security mailing list archives
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Date: Wed, 4 Aug 2010 07:18:03 -0400 From: Christoph Hellwig <hch@...radead.org> To: Dominik Brodowski <linux@...inikbrodowski.net>, Michael Monnerie <michael.monnerie@...it-management.at>, Christoph Hellwig <hch@...radead.org>, linux-raid@...r.kernel.org, xfs@....sgi.com, linux-kernel@...r.kernel.org, dm-devel@...hat.com Subject: Re: How to track down abysmal performance ata - raid1 - crypto - vg/lv - xfs 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? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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