Re: -mm seems significanty slower than mainline on kernbench

[Andrew Morton]

Martin Bligh <mbligh@xxxxxxxxxx> wrote:
>
> OK, I fixed the graphs so you can actually read them now ;-)

They're cute.

> http://test.kernel.org/perf/kernbench.elm3b6.png (x86_64 4x)
> http://test.kernel.org/perf/kernbench.moe.png (NUMA-Q)
> http://test.kernel.org/perf/kernbench.elm3b132.png (4x SMP ia32)
> 
> Both seems significantly slower on -mm (mm is green line)

Well, 1% slower.  -mm has permanent not-for-linus debug things, some of
which are expected to have a performance impact.  I don't know whether
they'd have a 1% impact though.

> If I look at diffprofile between 2.6.15 and 2.6.15-mm1, it just looks
> like we have lots more idle time.

Yes, we do.   It'd be useful to test -git7..

> You got strange scheduler changes in
> there, that you've been carrying for a long time (2.6.14-mm1 at least)? 
> or HZ piddling? See to be mainly getting much more idle time.

Yes, there are CPU scheduler changes, although much fewer than usual. 
Ingo, any suggestions as to a culprit?

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