linux-kernel - Re: [PATCH v2 1/3] x86, sched: check for counters overflow in frequency invariant accounting

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Message-ID: <1603369318.3162.21.camel@suse.cz>
Date:   Thu, 22 Oct 2020 14:21:58 +0200
From:   Giovanni Gherdovich <ggherdovich@...e.cz>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...e.de>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>, x86@...nel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Subject: Re: [PATCH v2 1/3] x86, sched: check for counters overflow in
 frequency invariant accounting

On Thu, 2020-10-22 at 10:46 +0200, Peter Zijlstra wrote:
> On Sun, May 31, 2020 at 08:24:51PM +0200, Giovanni Gherdovich wrote:
> 
> Hi Giovanni!
> 
> > +error:
> > +	pr_warn("Scheduler frequency invariance went wobbly, disabling!\n");
> > +	schedule_work(&disable_freq_invariance_work);
> > +}
> 
> I'm getting reports that we trigger this on resume. Would it make sense
> to hook into tsc_{save,restore}_sched_clock_state() (or somewhere near
> there) to reset the state (basically call init_counter_refs() again to
> ensure we're not having to deal with crazy ?

Hello,

right, if the counters keep running while the machine is suspended then the
current code thinks it's a runtime overflow. I'll prepare a patch to fix that,
thanks for the heads-up and the hint.


Giovanni