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SubjectRe: BFS vs. mainline scheduler benchmarks and measurements

* Jens Axboe <jens.axboe@oracle.com> wrote:

> On Tue, Sep 08 2009, Peter Zijlstra wrote:
> > On Tue, 2009-09-08 at 11:13 +0200, Jens Axboe wrote:
> > > And here's a newer version.
> >
> > I tinkered a bit with your proglet and finally found the
> > problem.
> >
> > You used a single pipe per child, this means the loop in
> > run_child() would consume what it just wrote out until it got
> > force preempted by the parent which would also get woken.
> >
> > This results in the child spinning a while (its full quota) and
> > only reporting the last timestamp to the parent.
>
> Oh doh, that's not well thought out. Well it was a quick hack :-)
> Thanks for the fixup, now it's at least usable to some degree.

What kind of latencies does it report on your box?

Our vanilla scheduler default latency targets are:

single-core: 20 msecs
dual-core: 40 msecs
quad-core: 60 msecs
opto-core: 80 msecs

You can enable CONFIG_SCHED_DEBUG=y and set it directly as well via
/proc/sys/kernel/sched_latency_ns:

echo 10000000 > /proc/sys/kernel/sched_latency_ns

Ingo


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