Date:	Wed, 23 May 2007 19:29:26 +0100
From:	Miguel Figueiredo <elmig@...ianpt.org>
To:	Bill Davidsen <davidsen@....com>
CC:	Ray Lee <ray-lk@...rabbit.org>,
	Linux Kernel M/L <linux-kernel@...r.kernel.org>,
	Con Kolivas <kernel@...ivas.org>
Subject: Re: Sched - graphic smoothness under load - cfs-v13 sd-0.48

Bill Davidsen wrote:
> 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.
> 

Hi Bill,

  the numbers i posted before are repeatable on that machine.


I did run, again, glitch1 on my laptop (T2500 CoreDuo, also Nvidia) 
please check: http://www.debianpt.org/~elmig/pool/kernel/20070523/



-- 

Com os melhores cumprimentos/Best regards,

Miguel Figueiredo
http://www.DebianPT.org
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