From: Vincent Guittot <vincent.guittot@linaro.org>
To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
dietmar.eggemann@arm.com, rostedt@goodmis.org,
bsegall@google.com, mgorman@suse.de, bristot@redhat.com,
linux-kernel@vger.kernel.org, rickyiu@google.com, odin@uged.al
Cc: sachinp@linux.vnet.ibm.com, naresh.kamboju@linaro.org,
Vincent Guittot <vincent.guittot@linaro.org>
Subject: [PATCH 0/3] sched/pelt: Don't sync hardly *_sum with *_avg
Date: Tue, 21 Dec 2021 10:46:50 +0100 [thread overview]
Message-ID: <20211221094653.10776-1-vincent.guittot@linaro.org> (raw)
Rick reported performance regressions in bugzilla because of cpu
frequency being lower than before:
https://bugzilla.kernel.org/show_bug.cgi?id=215045
He bisected the problem to:
commit 1c35b07e6d39 ("sched/fair: Ensure _sum and _avg values stay consistent")
More details are available in commit message of patch 1.
This patchset reverts the commit above and adds several checks when
propagating the changes in the hierarchy to make sure that we still have
coherent util_avg and util_sum.
Dietmar found a simple way to reproduce the WARN fixed by
commit 1c35b07e6d39 ("sched/fair: Ensure _sum and _avg values stay consistent")
by looping on hackbench in several different sched group levels.
This patchset as run on the reproducer with success but it probably needs
more tests by people who faced the WARN before.
The changes done on util_sum have been also applied to runnable_sum and
load_sum which faces the same rounding problem although this has not been
reflected in measurable performance impact.
Vincent Guittot (3):
sched/pelt: Don't sync hardly util_sum with uti_avg
sched/pelt: Don't sync hardly runnable_sum with runnable_avg
sched/pelt: Don't sync hardly runnable_sum with runnable_avg
kernel/sched/fair.c | 113 +++++++++++++++++++++++++++++---------------
1 file changed, 75 insertions(+), 38 deletions(-)
--
2.17.1
next reply other threads:[~2021-12-21 9:47 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-21 9:46 Vincent Guittot [this message]
2021-12-21 9:46 ` [PATCH 1/3] sched/pelt: Don't sync hardly util_sum with uti_avg Vincent Guittot
2021-12-21 9:46 ` [PATCH 2/3] sched/pelt: Don't sync hardly runnable_sum with runnable_avg Vincent Guittot
2021-12-21 9:46 ` [PATCH 3/3] " Vincent Guittot
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