From: Valentin Schneider <valentin.schneider@arm.com>
To: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Vincent Guittot <vincent.guittot@linaro.org>,
dietmar.eggemann@arm.com, patrick.bellasi@matbug.net,
lenb@kernel.org, linux-kernel@vger.kernel.org,
ionela.voinescu@arm.com, qperret@google.com,
viresh.kumar@linaro.org
Subject: Re: [PATCH] sched: Add schedutil overview
Date: Fri, 18 Dec 2020 14:25:33 +0000 [thread overview]
Message-ID: <jhjr1nnry1u.mognet@arm.com> (raw)
In-Reply-To: <20201218133655.GA10123@e123083-lin>
On 18/12/20 13:40, Morten Rasmussen wrote:
> On Fri, Dec 18, 2020 at 11:33:09AM +0000, Valentin Schneider wrote:
>> (also, does this need a word about runnable rt tasks => goto max?)
>
> What is actually the intended policy there? I thought it was goto max
> unless rt was clamped, but if I read the code correctly in
> schedutil_cpu_util() the current policy is only goto max if uclamp isn't
> in use at all, including cfs.
>
Right, so the policy pretty much is: by default, if there are runnable rt
tasks, goto max freq.
When uclamp isn't used, that's hardcoded.
When uclamp is in use, the default RT uclamp.min is 1024, so it "naturally"
drives frequency selection to the max when there are runnable RT tasks
(rq-aggregated uclamp.min == 1024). That default
(uclamp_util_min_rt_default) can be tweaked.
> The write-up looks good to me.
>
> Reviewed-by: Morten Rasmussen <morten.rasmussen@arm.com>
>
> Morten
next prev parent reply other threads:[~2020-12-18 14:26 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-18 10:32 [PATCH] sched: Add schedutil overview Peter Zijlstra
2020-12-18 11:33 ` Valentin Schneider
2020-12-18 13:40 ` Morten Rasmussen
2020-12-18 14:25 ` Valentin Schneider [this message]
2021-01-14 11:29 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
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