Messages in this thread | | | Date | Sun, 1 Feb 2009 11:04:10 +0100 | From | Ingo Molnar <> | Subject | Re: hackbench [pthread mode] regression with 2.6.29-rc3 |
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* 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
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