From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Paul Turner <pjt@google.com>
Cc: linux-kernel@vger.kernel.org, Venki Pallipadi <venki@google.com>,
Srivatsa Vaddagiri <vatsa@in.ibm.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
Subject: Re: [PATCH 12/16] sched: refactor update_shares_cpu() -> update_blocked_avgs()
Date: Thu, 12 Jul 2012 16:40:15 +0200 [thread overview]
Message-ID: <1342104015.28010.11.camel@twins> (raw)
In-Reply-To: <CAPM31RJoLTCM+DPpPk7bsks6Nb8mLNba9CC+Et4vBnMM3rdENw@mail.gmail.com>
On Wed, 2012-07-11 at 17:11 -0700, Paul Turner wrote:
> >> for_each_leaf_cfs_rq(rq, cfs_rq) {
> >> + __update_blocked_averages_cpu(cfs_rq->tg, rq->cpu);
> >>
> >> + /*
> >> + * Periodically release the lock so that a cfs_rq with many
> >> + * children cannot hold it for an arbitrary period of time.
> >> + */
> >> + if (num_updates++ % 20 == 0) {
> >> + raw_spin_unlock_irqrestore(&rq->lock, flags);
> >> + cpu_relax();
> >> + raw_spin_lock_irqsave(&rq->lock, flags);
> >
> > Gack.. that's not real pretty is it.. Esp. since we're still holding RCU
> > lock and are thus (mostly) still not preemptable.
> >
> > How much of a problem was this?, the changelog is silent on this.
>
> So the holding of RCU about these operations is nothing new (and
> indeed they should be much faster than before).
>
> As above, the bound is only for the crazy-large-numbers of cgroups
> case where we don't want to sit on with interrupts disabled forever.
> I suspect it wants to be larger, but picked a fairly conservative
> number to start with since I also think it's not a big performance
> factor either way.
How about you leave this ugly out for now (its unrelated to the rest of
the changes anyway).. and we can revisit this later?
next prev parent reply other threads:[~2012-07-12 14:40 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-28 2:24 [PATCH 00/16] Series short description Paul Turner
2012-06-28 2:24 ` [PATCH 08/16] sched: compute load contribution by a group entity Paul Turner
2012-06-28 2:24 ` [PATCH 02/16] sched: maintain per-rq runnable averages Paul Turner
2012-06-28 2:24 ` [PATCH 04/16] sched: maintain the load contribution of blocked entities Paul Turner
2012-06-29 1:27 ` Namhyung Kim
2012-06-28 2:24 ` [PATCH 03/16] sched: aggregate load contributed by task entities on parenting cfs_rq Paul Turner
2012-06-28 6:33 ` Namhyung Kim
2012-07-04 15:28 ` Peter Zijlstra
2012-07-06 14:53 ` Peter Zijlstra
2012-07-09 9:15 ` Ingo Molnar
2012-06-28 2:24 ` [PATCH 07/16] sched: aggregate total task_group load Paul Turner
2012-06-28 2:24 ` [PATCH 09/16] sched: normalize tg load contributions against runnable time Paul Turner
2012-06-29 7:26 ` Namhyung Kim
2012-07-04 19:48 ` Peter Zijlstra
2012-07-06 11:52 ` Peter Zijlstra
2012-07-12 1:08 ` Andre Noll
2012-07-12 0:02 ` Paul Turner
2012-07-06 12:23 ` Peter Zijlstra
2012-06-28 2:24 ` [PATCH 06/16] sched: account for blocked load waking back up Paul Turner
2012-06-28 2:24 ` [PATCH 05/16] sched: add an rq migration call-back to sched_class Paul Turner
2012-06-29 1:32 ` Namhyung Kim
2012-06-28 2:24 ` [PATCH 01/16] sched: track the runnable average on a per-task entitiy basis Paul Turner
2012-06-28 6:06 ` Namhyung Kim
2012-07-12 0:14 ` Paul Turner
2012-07-04 15:32 ` Peter Zijlstra
2012-07-12 0:12 ` Paul Turner
2012-06-28 2:24 ` [PATCH 12/16] sched: refactor update_shares_cpu() -> update_blocked_avgs() Paul Turner
2012-06-29 7:28 ` Namhyung Kim
2012-07-12 0:03 ` Paul Turner
2012-07-05 11:58 ` Peter Zijlstra
2012-07-12 0:11 ` Paul Turner
2012-07-12 14:40 ` Peter Zijlstra [this message]
2012-06-28 2:24 ` [PATCH 13/16] sched: update_cfs_shares at period edge Paul Turner
2012-06-28 2:24 ` [PATCH 15/16] sched: implement usage tracking Paul Turner
2012-06-28 2:24 ` [PATCH 16/16] sched: introduce temporary FAIR_GROUP_SCHED dependency for load-tracking Paul Turner
2012-06-28 2:24 ` [PATCH 10/16] sched: maintain runnable averages across throttled periods Paul Turner
2012-06-28 2:24 ` [PATCH 14/16] sched: make __update_entity_runnable_avg() fast Paul Turner
2012-07-04 15:41 ` Peter Zijlstra
2012-07-04 17:20 ` Peter Zijlstra
2012-07-09 20:18 ` Benjamin Segall
2012-07-10 10:51 ` Peter Zijlstra
2012-07-12 0:15 ` Paul Turner
2012-07-12 14:30 ` Peter Zijlstra
2012-07-04 16:51 ` Peter Zijlstra
2012-06-28 2:24 ` [PATCH 11/16] sched: replace update_shares weight distribution with per-entity computation Paul Turner
-- strict thread matches above, loose matches on Subject: below --
2012-08-23 14:14 [patch 00/16] sched: per-entity load-tracking pjt
2012-08-23 14:14 ` [patch 12/16] sched: refactor update_shares_cpu() -> update_blocked_avgs() pjt
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