lkml.org 
[lkml]   [2009]   [Sep]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: Poor desktop responsiveness with background I/O-operations
    From
    Date
    On Sun, 2009-09-20 at 17:22 -0700, Justin P. Mattock wrote:
    > Wow, at first I did not notice anything
    > from your *.sh script, but then a few moments
    > later, the system became vary sluggish. firefox
    > takes about 15 seconds to load. OS is mint linux
    > with the latest HEAD on an imac9,1.

    CFQ inherits IO priority from the parent on fork(), so nicing a shell or
    the dd should (and does) help a LOT. It also inherits the CPU scheduler
    class. I just checked, and IO does indeed inherit SCHED_IDLE as well as
    the RT classes (SCHED_BATCH does nothing). Setting the dd to SCHED_IDLE
    makes a big difference, as it should, so there's a bigger hammer than
    nice + ionice. SCHED_IDLE is CPU_adorable + IO_nicest.

    Anyway, the problem seems to have to have at least two facets:
    1. streaming IO causing pagecache reclaim. That problem doesn't seem
    to want to go away. Fixing that won't help 2 one bit though.

    2. reads are sync, more heavily affected by seek latency than writes.
    If the disk your binaries live on is seeking a lot, you pay a LOT.

    Hohum, IO + VM = haaaaard ;-)

    -Mike



    \
     
     \ /
      Last update: 2009-09-21 06:27    [W:4.471 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site