linux-kernel - Re: [PATCH 2/2] sched: cpufreq: use rt_avg as estimate of required RT CPU capacity

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: <alpine.DEB.2.20.1609021410340.5647@nanos>
Date:   Fri, 2 Sep 2016 14:17:25 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Juri Lelli <Juri.Lelli@....com>
cc:     Steve Muckle <steve.muckle@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Patrick Bellasi <patrick.bellasi@....com>
Subject: Re: [PATCH 2/2] sched: cpufreq: use rt_avg as estimate of required
 RT CPU capacity

On Fri, 2 Sep 2016, Juri Lelli wrote:
> On 01/09/16 14:48, Steve Muckle wrote:
> > On Wed, Aug 31, 2016 at 06:00:02PM +0100, Juri Lelli wrote:
> > > > Another problem is that we have many semi related knobs; we have the
> > > > global RT runtime limit knob, but that doesn't affect cpufreq (maybe it
> > > > should)
> > > 
> > > Maybe we could create this sort of link when using the cgroup RT
> > > throttling interface as well? It should still then fit well once we
> > > replace the underlying mechanism with DL reservations. And, AFAIK, the
> > > interface is used by Android folks already.
> > 
> > I'm not sure how the upper bounds can be used to infer CPU frequency...
> > On my Nexus 6p (an Android device), the global RT runtime limit
> > seems to be set at 950ms/1sec, the root cgroup is set to 800ms/1sec, and
> > bg_non_interactive is set at 700ms/1sec.
> > 
> 
> Right, unfortunately. Still too coarse grained (as Thomas is also saying
> in his last reply, if I read it correctly).

Yes, you do. It's a big hammer and really unsuitable for this kind of
mechanism.

> Doesn't pay off the added complexity I'm afraid.

Certainly not. And the only choice we have is heuristics. Heuristic is an
euphemism for saying that it cannot work.

Thanks,

	tglx