linux-kernel - [PATCH 0/2 v3] sched: improve spread of tasks during fork

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Message-Id: <1481216215-24651-1-git-send-email-vincent.guittot@linaro.org>
Date:   Thu,  8 Dec 2016 17:56:52 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     peterz@...radead.org, mingo@...nel.org,
        linux-kernel@...r.kernel.org, matt@...eblueprint.co.uk,
        Morten.Rasmussen@....com
Cc:     dietmar.eggemann@....com, kernellwp@...il.com,
        yuyang.du@...el.comc, umgwanakikbuti@...il.com,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH 0/2 v3] sched: improve spread of tasks during fork

Performance regression has been raised by Matt Fleming for fork intensive
bench like hackbench [1]
The patch 1/2 skips the spare_capacity test for fork task because the
utilization has not beed init yet.
The patch 2/2 takes into account load_avg for selecting CPU when
runnable_load of CPUs are close

Tests done by Matt Fleming show perf improvements with the patchset : [2] [3]

Changes since v2:
- renamed no_spare label to skip_spare
- changed load_avg test condition to prefer local cpu when load are similar
- added explanation for using absoluate margin instead of scale factor when
  comparing runnable_load

[1] https://lkml.org/lkml/2016/10/18/206
[2] https://lkml.org/lkml/2016/12/8/260
[3] https://lkml.org/lkml/2016/12/8/260

Vincent Guittot (2):
  sched: fix find_idlest_group for fork
  sched: use load_avg for selecting idlest group

 kernel/sched/fair.c | 54 +++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 44 insertions(+), 10 deletions(-)

-- 
2.7.4