Messages in this thread | | | Date | Fri, 15 Jun 2007 00:56:27 +0400 (MSD) | From | malc <> | Subject | Re: [patch] sched: accurate user accounting |
| |
On Thu, 14 Jun 2007, Ingo Molnar wrote:
> > * Vassili Karpov <av1474@comtv.ru> wrote: > >> Hello Ingo and others, >> >> After reading http://lwn.net/Articles/236485/ and noticing few >> refernces to accounting i decided to give CFS a try. With >> sched-cfs-v2.6.21.4-16 i get pretty weird results, it seems like >> scheduler is dead set on trying to move the processes to different >> CPUs/cores all the time. And with hog (manually tweaking the amount >> iterations) i get fairly strange resuls, first of all the process is >> split between two cores, secondly while integral load provided by the >> kernel looks correct, it's off by good 20 percent on each idividial >> core. >> >> (http://www.boblycat.org/~malc/apc/hog-cfs-v16.png) >> >> Thought this information might be of some interest. > > hm - what does 'hog' do, can i download hog.c from somewhere?
http://www.boblycat.org/~malc/apc/hog.c and also a in Documentation/cpu-load.txt.
> > the alternating balancing might be due to an uneven number of tasks > perhaps? If you have 3 tasks on 2 cores then there's no other solution > to achieve even performance of each task but to rotate them amongst the > cores.
One task, one thread. I have also tried to watch fairly demanding video (Elephants Dream in 1920x1080/MPEG4) with mplayer, and CFS moves the only task between cores almost every second.
>> P.S. How come the /proc/stat information is much closer to reality >> now? Something like what Con Kolivas suggested was added to >> sched.c? > > well, precise/finegrained accounting patches have been available for > years, the thing with CFS is that there we get them 'for free', because > CFS needs those metrics for its own logic. That's why this information > is much closer to reality now. But note: right now what is affected by > the changes in the CFS patches is /proc/PID/stat (i.e. the per-task > information that 'top' and 'ps' displays, _not_ /proc/stat) - but more > accurate /proc/stat could certainly come later on too.
Aha. I see, it's just that integral load for hog is vastly improved compared to vanilla 2.6.21 (then again some other tests are off by a few percent (at least), though they were fine with Con's patch (which was announced at the beginning of this thread))
-- vale - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |