linux-kernel - Re: [PATCH v2 1/6] sched: consolidate and cleanup access to CPU's max compute capacity

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Message-ID: <ZSPdeMzCzDRCIqUw@gmail.com>
Date:   Mon, 9 Oct 2023 13:01:12 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     linux@...linux.org.uk, catalin.marinas@....com, will@...nel.org,
        paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, sudeep.holla@....com,
        gregkh@...uxfoundation.org, rafael@...nel.org, mingo@...hat.com,
        peterz@...radead.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
        viresh.kumar@...aro.org, lukasz.luba@....com,
        ionela.voinescu@....com, pierre.gondois@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-pm@...r.kernel.org,
        conor.dooley@...rochip.com, suagrfillet@...il.com,
        ajones@...tanamicro.com, lftan@...nel.org
Subject: Re: [PATCH v2 1/6] sched: consolidate and cleanup access to CPU's
 max compute capacity


* Vincent Guittot <vincent.guittot@...aro.org> wrote:

> Remove struct rq cpu_capacity_orig field and use arch_scale_cpu_capacity()
> instead.
> 
> Scheduler uses 3 methods to get access to the CPU's max compute capacity:
> - arch_scale_cpu_capacity(cpu) which is the default way to get CPU's capacity.
> - cpu_capacity_orig field which is periodically updated with
>   arch_scale_cpu_capacity().
> - capacity_orig_of(cpu) which encapsulates rq->cpu_capacity_orig.
> 
> There is no real need to save the value returned by arch_scale_cpu_capacity()
> in struct rq. arch_scale_cpu_capacity() returns:
> - either a per_cpu variable.
> - or a const value for systems which have only one capacity.
> 
> Remove cpu_capacity_orig and use arch_scale_cpu_capacity() everywhere.
> 
> No functional changes.
> 
> some tests of Arm64
> small SMP device (hikey): no noticeable changes
> HMP device (RB5): hackbench shows minor improvement (1-2%)
> large smp (thx2): hackbench and tbench shows minor improvement (1%)
> 
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>
> 
> ---
>  Documentation/scheduler/sched-capacity.rst | 13 +++++++------
>  kernel/sched/core.c                        |  2 +-
>  kernel/sched/cpudeadline.c                 |  2 +-
>  kernel/sched/deadline.c                    |  4 ++--
>  kernel/sched/fair.c                        | 18 ++++++++----------
>  kernel/sched/rt.c                          |  2 +-
>  kernel/sched/sched.h                       |  6 ------
>  kernel/sched/topology.c                    |  7 +++++--
>  8 files changed, 25 insertions(+), 29 deletions(-)

I've applied patch #1 to tip:sched/core, thanks!

	Ingo