lkml.org 
[lkml]   [2010]   [Aug]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: How to track down abysmal performance ata - raid1 - crypto - vg/lv - xfs
    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


    \
     
     \ /
      Last update: 2010-08-04 13:27    [W:4.340 / U:0.116 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site