lkml.org 
[lkml]   [2009]   [Feb]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: hackbench [pthread mode] regression with 2.6.29-rc3

    * Peter Zijlstra <peterz@infradead.org> wrote:

    > On Sun, 2009-02-01 at 10:17 +0100, Peter Zijlstra wrote:
    > > On Sun, 2009-02-01 at 16:29 +0800, Lin Ming wrote:
    > > > > Bisect located below patch.
    > > > > commit 490dea45d00f01847ebebd007685d564aaf2cd98
    > > > > Author: Peter Zijlstra <peterz@infradead.org>
    > > > > Date: Mon Nov 24 17:06:57 2008 +0100
    > > > >
    > > > > itimers: remove the per-cpu-ish-ness
    > > > >
    > > > > Either we bounce once cacheline per cpu per tick, yielding n^2 bounces
    > > > > or we just bounce a single..
    > > > >
    > > > > Also, using per-cpu allocations for the thread-groups complicates the
    > > > > per-cpu allocator in that its currently aimed to be a fixed sized
    > > > > allocator and the only possible extention to that would be vmap based,
    > > > > which is seriously constrained on 32 bit archs.
    > > > >
    > > > >
    > > > > After above patch is reverted, hackbench result is restored.
    > > >
    > > > oltp has ~3% regression with 2.6.29-rc3 on 4core*2p stokley machine.
    > > > After above patch reverted, the regression disappeared.
    > >
    > > *sigh*, did they gain anything with introduction of the per-cpu crap?
    >
    > No it wouldn't have, I just missed something obvious,.. :-(
    >
    > I wish we never merged that crap...

    oh, it certainly had its use: it highlighted that we have crappy
    threading+timers code (on hackbench_pth) since the beginning of the Linux
    SMP times.

    Ingo


    \
     
     \ /
      Last update: 2009-02-01 11:07    [W:0.023 / U:2.008 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site