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SubjectRe: CFS review
Al Boldi wrote:
> Ingo Molnar wrote:
>> * Al Boldi <a1426z@gawab.com> wrote:
>>>>> The problem is that consecutive runs don't give consistent results
>>>>> and sometimes stalls. You may want to try that.
>>>> well, there's a natural saturation point after a few hundred tasks
>>>> (depending on your CPU's speed), at which point there's no idle time
>>>> left. From that point on things get slower progressively (and the
>>>> ability of the shell to start new ping tasks is impacted as well),
>>>> but that's expected on an overloaded system, isnt it?
>>> Of course, things should get slower with higher load, but it should be
>>> consistent without stalls.
>>>
>>> To see this problem, make sure you boot into /bin/sh with the normal
>>> VGA console (ie. not fb-console). Then try each loop a few times to
>>> show different behaviour; loops like:
>>>
>>> # for ((i=0; i<3333; i++)); do ping 10.1 -A > /dev/null & done
>>>
>>> # for ((i=0; i<3333; i++)); do nice -99 ping 10.1 -A > /dev/null & done
>>>
>>> # { for ((i=0; i<3333; i++)); do
>>> ping 10.1 -A > /dev/null &
>>> done } > /dev/null 2>&1
>>>
>>> Especially the last one sometimes causes a complete console lock-up,
>>> while the other two sometimes stall then surge periodically.
>> ok. I think i might finally have found the bug causing this. Could you
>> try the fix below, does your webserver thread-startup test work any
>> better?
>
> It seems to help somewhat, but the problem is still visible. Even v20.3 on
> 2.6.22.5 didn't help.
>
> It does look related to ia-boosting, so I turned off __update_curr like Roman
> mentioned, which had an enormous smoothing effect, but then nice levels
> completely break down and lockup the system.
>
> 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.

--
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
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