Re: Sched - graphic smoothness under load - cfs-v13 sd-0.48

Bill Davidsen
2007-05-23T13:09:35Z

I was unable to reproduce the numbers Miguel generated, comments below.
The -ck2 patch seems to run nicely, although the memory repopulation
from swap would be most useful on system which have a lot of memory
pressure.

Bill Davidsen wrote:
> Miguel Figueiredo wrote:
>>
>> Hi Bill,
>>
>> if i've understood correctly the script runs glxgears for 43 seconds
>> and in that time generates random numbers in a random number of times
>> (processes, fork and forget), is that it?
>>
> No, I haven't made it clear. A known number (default four) of xterms
> are started, each of which calculates random numbers and prints them,
> using much CPU time and causing a lot of scrolling. At the same time
> glxgears is running, and the smoothness (or not) is observed manually.
> The script records raw data on the number of frames per second and the
> number of random numbers calculated by each shell. Since these are
> FAIR schedulers, the variance between the scripts, and between
> multiple samples from glxgears is of interest. To avoid startup
> effects the glxgears value from the first sample is reported
> separately and not included in the statistics.
>
> I looked at your results, and they are disturbing to say the least, it
> appears that using the ck2 scheduler glxgears stopped for all
> practical purposes. You don't have quite the latest glitch1, the new
> one runs longer and allows reruns to get several datasets, but the
> results still show very slow gears and a large difference between the
> work done by the four shells. That's not a good result, how did the
> system feel?
>> You find the data, for 2.6.21-{cfs-v13, ck2} in
>> http://www.debianpt.org/~elmig/pool/kernel/20070522/
>>
> Thank you, these results are very surprising, and I would not expect
> the system to be pleasing the use under load, based on this.
>> Here's the funny part...
>>
>> Lets call:
>>
>> a) to "random number of processes run while glxgears is running",
>> gl_fairloops file
>>
> It's really the relative work done by identical processes, hopefully
> they are all nearly the same, magnitude is interesting but related to
> responsiveness rather than fairness.
>> b) to "generated frames while running a burst of processes" aka
>> "massive and uknown amount of operations in one process", gl_gears file
>>
> Well, top or ps will give you a good idea of processing, but it tried
> to use all of one CPU if allowed. Again, similarity of samples
> reflects fairness and magnitude reflects work done.
>> kernel 2.6.21-cfs-v13 2.6.21-ck2
>> a) 194464 254669 b) 54159 124
>>
>>
> Everyone seems to like ck2, this makes it look as if the video display
> would be really pretty unusable. While sd-0.48 does show an occasional
> video glitch when watching video under heavy load, it's annoying
> rather than unusable.
>
I spent a few hours running the -ck2 patch, and I didn't see any numbers
like yours. What I did see is going up with my previous results as
http://www.tmr.com/~davidsen/sched_smooth_04.html. While there were
still some minor pauses in glxgears with my test, performance was very
similar to the sd-0.48 results. And I did try watching video with high
load, without problems. Only when I run a lot of other screen-changing
processes can I see pauses in the display.
> Your subjective impressions would be helpful, and you may find that
> the package in the www.tmr.com/~public/source is slightly easier to
> use and gives more stable results. The documentation suggests the way
> to take samples (the way I did it) but if you feel more or longer
> samples would help it is tunable.
>
> I added Con to the cc list, he may have comments or suggestions
> (against the current versions, please). Or he may feel that video
> combined with other heavy screen updating is unrealistic or not his
> chosen load. I'm told the load is similar to games which use threads
> and do lots of independent action, if that's a reference.
>
I'll include the -ck2 patch in my testing on other hardware.

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