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SubjectRe: hackbench [pthread mode] regression with 2.6.29-rc3
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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...



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