Messages in this thread | | | Date | Tue, 8 Mar 2011 09:27:59 +0530 | From | Balbir Singh <> | Subject | Re: [CFS Bandwidth Control v4 0/7] Introduction |
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* jacob pan <jacob.jun.pan@linux.intel.com> [2011-02-25 05:06:46]:
> On Fri, 25 Feb 2011 02:03:54 -0800 > Paul Turner <pjt@google.com> wrote: > > > On Thu, Feb 24, 2011 at 4:11 PM, jacob pan > > <jacob.jun.pan@linux.intel.com> wrote: > > > On Tue, 15 Feb 2011 19:18:31 -0800 > > > Paul Turner <pjt@google.com> wrote: > > > > > >> Hi all, > > >> > > >> Please find attached v4 of CFS bandwidth control; while this rebase > > >> against some of the latest SCHED_NORMAL code is new, the features > > >> and methodology are fairly mature at this point and have proved > > >> both effective and stable for several workloads. > > >> > > >> As always, all comments/feedback welcome. > > >> > > > > > > Hi Paul, > > > > > > Your patches provide a very useful but slightly different feature > > > for what we need to manage idle time in order to save power. What we > > > need is kind of a quota/period in terms of idle time. I have been > > > playing with your patches and noticed that when the cgroup cpu usage > > > exceeds the quota the effect of throttling is similar to what I have > > > been trying to do with freezer subsystem. i.e. freeze and thaw at > > > given period and percentage runtime. > > > https://lkml.org/lkml/2011/2/15/314 > > > > > > Have you thought about adding such feature (please see detailed > > > description in the link above) to your patches? > > > > > > > So reading the description it seems like rooting everything in a > > 'freezer' container and then setting up a quota of > > > > (1 - frozen_percentage) * nr_cpus * frozen_period * sec_to_usec > > > I guess you meant frozen_percentage is less than 1, i.e. 90 is .90. my > code treat 90 as 90. just a clarification. > > on a period of > > > > frozen_period * sec_to_usec > > > > Would provide the same functionality. Is there other unduplicated > > functionality beyond this? > Do you mean the same functionality as your patch? Not really, since my > approach will stop the tasks based on hard time slices. But seems your > patch will allow them to run if they don't exceed the quota. Am i > missing something? > That is the only functionality difference i know. > > Like the reviewer of freezer patch pointed out, it is a more logical > fit to implement such feature in scheduler/yours in stead of freezer. So > i am wondering if your patch can be expended to include limiting quota > on real time. >
Do you mean sched rt group controller? Have you looked at cpu.rt_runtime_us and cpu.rt_perioud_us?
> I did a comparison study between CFS BW and freezer patch on skype with > identical quota setting as you pointed out earlier. Both use 2 sec > period and .2 sec quota (10%). Skype typically uses 5% of the CPU on my > system when placing a call(below cfs quota) and it wakes up every 100ms > to do some quick checks. Then I run skype in cpu then freezer cgroup > (with all its children). Here is my result based on timechart and > powertop. > > patch name wakeups skype call? > ------------------------------------------------------------------ > CFS BW 10/sec yes > freezer 1/sec no >
Is this good or bad for CFS BW?
-- Three Cheers, Balbir
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