lkml.org 
[lkml]   [2004]   [Dec]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Time sliced CFQ io scheduler
    On Wed, Dec 08 2004, Nick Piggin wrote:
    > On Wed, 2004-12-08 at 07:58 +0100, Jens Axboe wrote:
    > > On Wed, Dec 08 2004, Nick Piggin wrote:
    > > > On Tue, 2004-12-07 at 18:25 -0800, Andrew Morton wrote:
    >
    > > > I think we could detect when a disk asks for more than, say, 4
    > > > concurrent requests, and in that case turn off read anticipation
    > > > and all the anti-starvation for TCQ by default (with the option
    > > > to force it back on).
    > >
    > > CFQ only allows a certain depth a the hardware level, you can control
    > > that. I don't think you should drop the AS behaviour in that case, you
    > > should look at when the last request comes in and what type it is.
    > >
    > > With time sliced cfq I'm seeing some silly SCSI disk behaviour as well,
    > > it gets harder to get good read bandwidth as the disk is trying pretty
    > > hard to starve me. Maybe killing write back caching would help, I'll
    > > have to try.
    > >
    >
    > I "fixed" this in AS. It gets (or got, last time we checked, many months
    > ago) pretty good read latency even with a big write and a very large
    > tag depth.

    This problem was also caused by the dispatch sort bug. So you were
    right, it was 'some little bug' in the code :)

    --
    Jens Axboe

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 14:08    [W:0.020 / U:96.400 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site