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SubjectRe: CFS review
Ingo Molnar wrote:
> * Bill Davidsen <davidsen@tmr.com> wrote:
>
>
>>> There is another way to show the problem visually under X
>>> (vesa-driver), by starting 3 gears simultaneously, which after
>>> laying them out side-by-side need some settling time before
>>> smoothing out. Without __update_curr it's absolutely smooth from
>>> the start.
>>>
>> I posted a LOT of stuff using the glitch1 script, and finally found a
>> set of tuning values which make the test script run smooth. See back
>> posts, I don't have them here.
>>
>
> but you have real 3D hw and DRI enabled, correct? In that case X uses up
> almost no CPU time and glxgears makes most of the processing. That is
> quite different from the above software-rendering case, where X spends
> most of the CPU time.
>

No, my test machine for that is a compile server, and uses the built-in
motherboard graphics which are very limited. This is not in any sense a
graphics powerhouse, it is used to build custom kernels and
applications, and for testing of kvm and xen, and I grabbed it because
it had the only Core2 CPU I could reboot to try new kernel versions and
"from cold boot" testing, discovered the graphics smoothness issue by
having several windows open on compiles, and developed the glitch1
script as a way to reproduce it.

The settings I used, features=14, granularity=500000, work to improve
smoothness on other machines for other uses, but they do seem to impact
performance for compiles, video processing, etc, so they are not optimal
for general use. I regard the existence of these tuning knobs as one of
the real strengths of CFS, when you change the tuning it has a visible
effect.

--
bill davidsen <davidsen@tmr.com>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979

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