linux-kernel - Re: [PATCH v3 3/7] sched: throttle cfs_rq entities which exceed their local quota

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Date:	Wed, 13 Oct 2010 16:00:11 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Paul Turner <pjt@...gle.com>
Cc:	bharata@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	Dhaval Giani <dhaval.giani@...il.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Herbert Poetzl <herbert@...hfloor.at>,
	Avi Kivity <avi@...hat.com>,
	Chris Friesen <cfriesen@...tel.com>,
	Paul Menage <menage@...gle.com>,
	Mike Waychison <mikew@...gle.com>,
	Nikhil Rao <ncrao@...gle.com>
Subject: Re: [PATCH v3 3/7] sched: throttle cfs_rq entities which exceed
 their local quota

On Tue, 12 Oct 2010 23:44:29 -0700
Paul Turner <pjt@...gle.com> wrote:

> On Tue, Oct 12, 2010 at 11:34 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@...fujitsu.com> wrote:
> > On Tue, 12 Oct 2010 13:22:02 +0530
> > Bharata B Rao <bharata@...ux.vnet.ibm.com> wrote:

> >>  /*
> >>   * Re-compute the task group their per cpu shares over the given domain.
> >>   * This needs to be done in a bottom-up fashion because the rq weight of a
> >> @@ -1688,7 +1691,14 @@ static int tg_shares_up(struct task_grou
> >>       usd_rq_weight = per_cpu_ptr(update_shares_data, smp_processor_id());
> >>
> >>       for_each_cpu(i, sched_domain_span(sd)) {
> >> -             weight = tg->cfs_rq[i]->load.weight;
> >> +             /*
> >> +              * bandwidth throttled entities cannot contribute to load
> >> +              * balance
> >> +              */
> >> +             if (!cfs_rq_throttled(tg->cfs_rq[i]))
> >> +                     weight = tg->cfs_rq[i]->load.weight;
> >> +             else
> >> +                     weight = 0;
> >
> > cpu.share and bandwidth control can't be used simultaneously or...
> > is this fair ? I'm not familiar with scheduler but this allows boost this tg.
> > Could you add a brief documentaion of a spec/feature. in the next post ?
> >
> 
> Bandwidth control is orthogonal to shares, shares continue controls
> distribution of bandwidth when within quota.  Bandwidth control only
> has 'perceivable' effect when you exceed your reservation within a
> quota period.
> 
> What the above is doing is removing any throttled entities from the
> load-balancer's weight calculations (based on contribution from
> throttled entities) since these entities are already dequeued and
> cannot be balanced.
> 
> Or have I misunderstood your question?
> 

Thank you for quick reply.
It seems I don't undestand what "cfs_rq_throttled()==1" means.

Thanks,
-Kame

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