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From: Vincent Guittot <vincent.guittot@linaro.org>
To: peterz@infradead.org, mingo@kernel.org, linux-kernel@vger.kernel.org
Cc: dietmar.eggemann@arm.com, Morten.Rasmussen@arm.com,
	yuyang.du@intel.com, pjt@google.com, bsegall@google.com,
	Vincent Guittot <vincent.guittot@linaro.org>
Subject: [PATCH 0/2] sched/cfs: make util/load_avg stable
Date: Wed, 19 Apr 2017 18:44:15 +0200	[thread overview]
Message-ID: <1492620257-30109-1-git-send-email-vincent.guittot@linaro.org> (raw)
In-Reply-To: <1492619370-29246-1-git-send-email-vincent.guittot@linaro.org>

In the current implementation of load/util_avg, we assume that the ongoing
time segment has fully elapsed and util/load_sum is divided by LOAD_AVG_MAX,
even if part of the time segment still remains to run . As a consequence,
this remaining part is considered as idle time and generates unexpected
variations of util_avg of a busy CPU in the range ]1002..1024[ whereas
util_avg should stay at 1023.

The 1st patch implements Peter's proposal to remove the contribution of the
current time segment when computing the util/load_avg. The 2nd one keeps
using the current segment but update the max value instead. Both solutions
make load/util_avg being stable with the advantage of using the most up to
date value for the 2nd patch. I have split it into 2 patches to show the 2
versions but if the 2nd patch looks ok, we should probably squashed them into
one.

Vincent Guittot (2):
  sched/cfs: make util/load_avg more stable
  sched/cfs: take into account current segment

 kernel/sched/fair.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

-- 
2.7.4

  parent reply	other threads:[~2017-04-19 17:11 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-19 16:29 Vincent Guittot
2017-04-19 16:29 ` [PATCH 1/2] sched/cfs: make util/load_avg more stable Vincent Guittot
2017-04-19 16:29 ` [PATCH 2/2] sched/cfs: take into account current time segment Vincent Guittot
2017-04-19 16:44 ` Vincent Guittot [this message]
2017-04-19 16:44   ` [PATCH 1/2] sched/cfs: make util/load_avg more stable Vincent Guittot
2017-04-19 16:44   ` [PATCH 2/2] sched/cfs: take into account current time segment Vincent Guittot
2017-04-19 16:54 ` [PATCH v2] sched/cfs: make util/load_avg more stable Vincent Guittot
2017-04-25 11:05   ` Dietmar Eggemann
2017-04-25 12:40     ` Vincent Guittot
2017-04-25 14:53       ` Dietmar Eggemann
2017-04-25 15:17         ` Vincent Guittot

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