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SubjectRe: Epic regression in throughput since v2.6.23

* Serge Belyshev <belyshev@depni.sinp.msu.ru> wrote:

> Ingo Molnar <mingo@elte.hu> writes:
>
> > Thanks!
> >
> > I think we found the reason for that regression - would you mind
> > to re-test with latest -tip, e157986 or later?
> >
> > If that works for you i'll describe our theory.
> >
>
> Good job -- seems to work, thanks. Regression is still about 3%
> though: http://img3.imageshack.us/img3/5335/epicbfstip.png

Ok, thanks for the update. The problem is that i've run out of
testsystems that can reproduce this. So we need your help to debug
this directly ...

A good start would be to post the -tip versus BFS "perf stat"
measurement results:

perf stat --repeat 3 make -j4 bzImage

And also the -j8 perf stat result, so that we can see what the
difference is between -j4 and -j8.

Note: please check out latest tip and do:

cd tools/perf/
make -j install

To pick up the latest 'perf' tool. In particular the precision of
--repeat has been improved recently so you want that binary from
-tip even if you measure vanilla .31 or .31 based BFS.

Also, it would be nice if you could send me your kernel config -
maybe it's some config detail that keeps me from being able to
reproduce these results. I havent seen a link to a config in your
mails (maybe i missed it - these threads are voluminous).

Ingo


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