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? -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
