Re: [patch] CFS scheduler, -v19

Bill Davidsen
2007-07-13T21:20:33Z

Ingo Molnar wrote:
> * Bill Davidsen <davidsen@tmr.com> wrote:
>
>>> I've taken mainline git tree (freshly integrated CFS!) out for a
>>> multimedia spin. I tested watching movies and listenign to music in
>>> the presence of various sleep/burn loads, pure burn loads, and mixed
>>> loads. All was peachy here.. I saw no frame drops or sound skips or
>>> other artifacts under any load where the processor could possibly
>>> meet demand.
>> I would agree with preliminary testing, save that if you get a lot of
>> processes updating the screen at once, there seems to be a notable
>> case of processes getting no CPU for 100-300ms, followed by a lot of
>> CPU.
>>
>> I see this clearly with the "glitch1" test with four scrolling xterms
>> and glxgears, but also watching videos with little busy processes on
>> the screen. The only version where I never see this in test or with
>> real use is cfs-v13.
>
> just as a test, does this go away if you:
>
> renice -20 pidof `Xorg`
>
> i.e. is this connected to the way X is scheduled?
>
Doing this slows down the display rates, but doesn't significantly help
the smoothness of the gears.

> Another thing to check would be whether it goes away if you set the
> granularity to some really finegrained value:
>
> echo 0 > /proc/sys/kernel/sched_wakeup_granularity_ns
> echo 500000 > /proc/sys/kernel/sched_granularity_ns
>
> this really pushes things - but it tests the theory whether this is
> related to granularity.
>
I didn't test this with standard Xorg priority, I should go back and try
that. But it didn't really make much difference. The gears and scrolling
xterms ran slower with Xorg at -20 with any sched settings. I'll do that
as soon as a build finishes and I can reboot.

I should really go back to 2.6.21.6, 2.6.22 has many bizarre behaviors
with FC6. Automount starts taking 30% of CPU (unused at the moment), the
sensors applet doesn't work, etc. I hope over the weekend I can get bug
reports out on all this, but there are lots of non-critical oddities.
> Ingo

--
Bill Davidsen <davidsen@tmr.com>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot