Messages in this thread | | | Date | Wed, 09 Sep 2009 12:05:22 +0300 | From | Nikos Chantziaras <> | Subject | Re: BFS vs. mainline scheduler benchmarks and measurements |
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On 09/09/2009 11:52 AM, Mike Galbraith wrote: > On Wed, 2009-09-09 at 08:13 +0200, Ingo Molnar wrote: >> * 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 > > He would also need to lower min_granularity, otherwise, it'd be larger > than the whole latency target.
Thank you for mentioning min_granularity. After:
echo 10000000 > /proc/sys/kernel/sched_latency_ns echo 2000000 > /proc/sys/kernel/sched_min_granularity_ns
I can clearly see an improvement: animations that are supposed to be fluid "skip" much less now, and in one occasion (simply moving the video window around) have been eliminated completely. However, there seems to be a side effect from having CONFIG_SCHED_DEBUG enabled; things seem to be generally a tad more "jerky" with that option enabled, even when not even touching the latency and granularity defaults.
I'll try the patch you posted and see if this further improves things.
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