linux-kernel - [RFC PATCH 0/2] sched/fair migration reduction features

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Message-Id: <20231018204511.1563390-1-mathieu.desnoyers@efficios.com>
Date:   Wed, 18 Oct 2023 16:45:09 -0400
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Ingo Molnar <mingo@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Swapnil Sapkal <Swapnil.Sapkal@....com>,
        Aaron Lu <aaron.lu@...el.com>, Chen Yu <yu.c.chen@...el.com>,
        Tim Chen <tim.c.chen@...el.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        "Gautham R . Shenoy" <gautham.shenoy@....com>, x86@...nel.org
Subject: [RFC PATCH 0/2] sched/fair migration reduction features

Hi,

This series introduces two new scheduler features: UTIL_FITS_CAPACITY
and SELECT_BIAS_PREV. When used together, they achieve a 47% speedup of
a hackbench workload which leaves some idle CPU time on a 192-core AMD
EPYC.

The main metrics which are significantly improved are:

- cpu-migrations are reduced by 93%,
- CPU utilization is increased by 22%.

Feedback is welcome. I am especially interested to learn whether this
series has positive or detrimental effects on performance of other
workloads.

Thanks,

Mathieu

Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Valentin Schneider <vschneid@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Ben Segall <bsegall@...gle.com>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Swapnil Sapkal <Swapnil.Sapkal@....com>
Cc: Aaron Lu <aaron.lu@...el.com>
Cc: Chen Yu <yu.c.chen@...el.com>
Cc: Tim Chen <tim.c.chen@...el.com>
Cc: K Prateek Nayak <kprateek.nayak@....com>
Cc: Gautham R . Shenoy <gautham.shenoy@....com>
Cc: x86@...nel.org

Mathieu Desnoyers (2):
  sched/fair: Introduce UTIL_FITS_CAPACITY feature
  sched/fair: Introduce SELECT_BIAS_PREV to reduce migrations

 kernel/sched/fair.c     | 77 ++++++++++++++++++++++++++++++++++++-----
 kernel/sched/features.h | 12 +++++++
 kernel/sched/sched.h    |  5 +++
 3 files changed, 86 insertions(+), 8 deletions(-)

-- 
2.39.2