Re: [Bugme-new] [Bug 15618] New: 2.6.18->2.6.32->2.6.33 hugeregression in performance

[Andrew Morton]

On Tue, 23 Mar 2010 18:34:09 +0100
Ingo Molnar <mingo@xxxxxxx> wrote:

> 
> It shows a very brutal amount of page fault invoked mmap_sem spinning 
> overhead.
> 

Yes.  Note that we fall off a cliff at nine threads on a 16-way.  As
soon as a core gets two threads scheduled onto it?  Probably triggered
by an MM change, possibly triggered by a sched change which tickled a
preexisting MM shortcoming.  Who knows.

Anton, we have an executable binary in the bugzilla report but it would
be nice to also have at least a description of what that code is
actually doing.  A quick strace shows quite a lot of mprotect activity.
A pseudo-code walkthrough, perhaps?

Thanks.
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