linux-kernel - Re: [PATCH] cpufreq: schedutil: rate limits for SCHED

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <11598161.veS9VGWB8G@aspire.rjw.lan>
Date:   Fri, 09 Feb 2018 11:36:30 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Claudio Scordino <claudio@...dence.eu.com>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Todd Kjos <tkjos@...roid.com>,
        Joel Fernandes <joelaf@...gle.com>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: schedutil: rate limits for SCHED_DEADLINE

On Friday, February 9, 2018 9:02:34 AM CET Claudio Scordino wrote:
> Hi Viresh,
> 
> Il 09/02/2018 04:51, Viresh Kumar ha scritto:
> > On 08-02-18, 18:01, Claudio Scordino wrote:
> >> When the SCHED_DEADLINE scheduling class increases the CPU utilization,
> >> we should not wait for the rate limit, otherwise we may miss some deadline.
> >>
> >> Tests using rt-app on Exynos5422 have shown reductions of about 10% of deadline
> >> misses for tasks with low RT periods.
> >>
> >> The patch applies on top of the one recently proposed by Peter to drop the
> >> SCHED_CPUFREQ_* flags.
> >>

[cut]

> 
> > 
> > Is it possible to (somehow) check here if the DL tasks will miss
> > deadline if we continue to run at current frequency? And only ignore
> > rate-limit if that is the case ?
> 
> I need to think further about it.

That would be my approach FWIW.

Increasing the frequency beyond what is necessary means wasting energy
in any case.

Thanks,
Rafael