On Wed, Aug 04, 2010 at 07:18:03AM -0400, Christoph Hellwig wrote: > 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? 2 CPUs overall: Cpu(s): 1.0%us, 5.7%sy, 0.0%ni, 44.8%id, 47.0%wa, 0.0%hi, 1.5%si, 0.0%st Thanks & best, Dominik -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
