Re: BFS vs. mainline scheduler benchmarks and measurements
From: Ingo Molnar
Date: Wed Sep 09 2009 - 02:13:42 EST
* Jens Axboe <jens.axboe@xxxxxxxxxx> wrote:
>
On Tue, Sep 08 2009, Peter Zijlstra wrote:
>
> On Tue, 2009年09月08日 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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