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From: Benjamin Segall <bsegall@google.com>
To: "Jan H. Schönherr" <schnhrr@cs.tu-berlin.de>
Cc: pjt@google.com, linux-kernel@vger.kernel.org,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Ingo Molnar <mingo@elte.hu>,
	Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@in.ibm.com>,
	Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>,
	Venki Pallipadi <venki@google.com>,
	Mike Galbraith <efault@gmx.de>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>,
	Morten Rasmussen <Morten.Rasmussen@arm.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Namhyung Kim <namhyung@kernel.org>
Subject: Re: [patch 11/16] sched: replace update_shares weight distribution with per-entity computation
Date: Mon, 24 Sep 2012 13:39:36 -0700	[thread overview]
Message-ID: <xm26vcf3b1fb.fsf@sword-of-the-dawn.mtv.corp.google.com> (raw)
In-Reply-To: <5060B82B.1050206@cs.tu-berlin.de> ("Jan H. =?utf-8?Q?Sch?= =?utf-8?Q?=C3=B6nherr=22's?= message of "Mon, 24 Sep 2012 21:44:43 +0200")

blocked_load_avg ~= \sum_child child.runnable_avg_sum/child.runnable_avg_period * child.weight

The thought was: So if all the children have hit zero runnable_avg_sum
(or in the case of a child task, will when they wake up), then
blocked_avg sum should also hit zero at the same and we're in theory
fine.

However, child load can be significantly larger than even the maximum
value of runnable_avg_sum (and you can get a full contribution off a new
task with only one tick of runnable_avg_sum anyway...), so
runnable_avg_sum can hit zero first due to rounding. We should case on
runnable_avg_sum || blocked_load_avg.


As a side note, currently decay_load uses SRR, which means none of these
will hit zero anyway if updates occur more often than once per 32ms. I'm
not sure how we missed /that/, but fixes incoming.

Thanks,
Ben


  reply	other threads:[~2012-09-24 20:39 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-23 14:14 [patch 00/16] sched: per-entity load-tracking pjt
2012-08-23 14:14 ` [patch 01/16] sched: track the runnable average on a per-task entitiy basis pjt
2012-08-24  8:20   ` Namhyung Kim
2012-08-28 22:12     ` Paul Turner
2012-10-24  9:43   ` [tip:sched/core] sched: Track the runnable average on a per-task entity basis tip-bot for Paul Turner
2012-10-25  3:28     ` li guang
2012-10-25 16:58       ` Benjamin Segall
2012-08-23 14:14 ` [patch 02/16] sched: maintain per-rq runnable averages pjt
2012-10-24  9:44   ` [tip:sched/core] sched: Maintain " tip-bot for Ben Segall
2012-10-28 10:12   ` [patch 02/16] sched: maintain " Preeti Murthy
2012-10-29 17:38     ` Benjamin Segall
2012-11-07  8:28       ` Preeti U Murthy
2012-08-23 14:14 ` [patch 03/16] sched: aggregate load contributed by task entities on parenting cfs_rq pjt
2012-10-24  9:45   ` [tip:sched/core] sched: Aggregate " tip-bot for Paul Turner
2012-08-23 14:14 ` [patch 04/16] sched: maintain the load contribution of blocked entities pjt
2012-10-24  9:46   ` [tip:sched/core] sched: Maintain " tip-bot for Paul Turner
2012-08-23 14:14 ` [patch 05/16] sched: add an rq migration call-back to sched_class pjt
2012-10-24  9:47   ` [tip:sched/core] sched: Add " tip-bot for Paul Turner
2012-08-23 14:14 ` [patch 06/16] sched: account for blocked load waking back up pjt
     [not found]   ` <CAM4v1pO8SPCmqJTTBHpqwrwuO7noPdskg0RSooxyPsWoE395_A@mail.gmail.com>
2012-09-04 17:29     ` Benjamin Segall
2012-10-24  9:48   ` [tip:sched/core] sched: Account " tip-bot for Paul Turner
2012-08-23 14:14 ` [patch 07/16] sched: aggregate total task_group load pjt
2012-10-24  9:49   ` [tip:sched/core] sched: Aggregate " tip-bot for Paul Turner
2012-08-23 14:14 ` [patch 08/16] sched: compute load contribution by a group entity pjt
2012-10-24  9:50   ` [tip:sched/core] sched: Compute " tip-bot for Paul Turner
2012-08-23 14:14 ` [patch 09/16] sched: normalize tg load contributions against runnable time pjt
2012-10-24  9:51   ` [tip:sched/core] sched: Normalize " tip-bot for Paul Turner
2012-08-23 14:14 ` [patch 10/16] sched: maintain runnable averages across throttled periods pjt
2012-10-24  9:52   ` [tip:sched/core] sched: Maintain " tip-bot for Paul Turner
2012-08-23 14:14 ` [patch 11/16] sched: replace update_shares weight distribution with per-entity computation pjt
2012-09-24 19:44   ` "Jan H. Schönherr"
2012-09-24 20:39     ` Benjamin Segall [this message]
2012-10-02 21:14       ` Paul Turner
2012-10-24  9:53   ` [tip:sched/core] sched: Replace " tip-bot for Paul Turner
2012-08-23 14:14 ` [patch 12/16] sched: refactor update_shares_cpu() -> update_blocked_avgs() pjt
2012-10-24  9:54   ` [tip:sched/core] sched: Refactor " tip-bot for Paul Turner
2012-08-23 14:14 ` [patch 13/16] sched: update_cfs_shares at period edge pjt
2012-09-24 19:51   ` "Jan H. Schönherr"
2012-10-02 21:09     ` Paul Turner
2012-10-24  9:55   ` [tip:sched/core] sched: Update_cfs_shares " tip-bot for Paul Turner
2012-08-23 14:14 ` [patch 14/16] sched: make __update_entity_runnable_avg() fast pjt
2012-08-24  8:28   ` Namhyung Kim
2012-08-28 22:18     ` Paul Turner
2012-10-24  9:56   ` [tip:sched/core] sched: Make " tip-bot for Paul Turner
2012-08-23 14:14 ` [patch 15/16] sched: implement usage tracking pjt
2012-10-19 12:18   ` Vincent Guittot
2012-08-23 14:14 ` [patch 16/16] sched: introduce temporary FAIR_GROUP_SCHED dependency for load-tracking pjt
2012-10-24  9:57   ` [tip:sched/core] sched: Introduce " tip-bot for Paul Turner
2012-09-24  9:30 ` [patch 00/16] sched: per-entity load-tracking "Jan H. Schönherr"
2012-09-24 17:16   ` Benjamin Segall
2012-10-05  9:07     ` Paul Turner
2012-11-26 13:08 ` Jassi Brar
2012-12-20  7:39   ` Stephen Boyd
2012-12-20  8:08     ` Jassi Brar
  -- strict thread matches above, loose matches on Subject: below --
2012-06-28  2:24 [PATCH 00/16] Series short description Paul Turner
2012-06-28  2:24 ` [PATCH 11/16] sched: replace update_shares weight distribution with per-entity computation Paul Turner

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