linux-kernel - Re: Fwd: Intel hybrid CPU scheduler always prefers E cores

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Date:   Wed, 29 Nov 2023 10:05:42 -0500
From:   srinivas pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Ramses <ramses@...l-founded.dev>
Cc:     Bagas Sanjaya <bagasdotme@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Regressions <regressions@...ts.linux.dev>,
        Linux Power Management <linux-pm@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Yu Chen <yu.c.chen@...el.com>
Subject: Re: Fwd: Intel hybrid CPU scheduler always prefers E cores

On Tue, 2023-11-28 at 15:10 -0800, Tim Chen wrote:
> On Tue, 2023-11-28 at 23:33 +0100, Ramses wrote:
> 
> > I applied the patch on top of 6.6.2, but unfortunately I see more
> > or less the same behaviour as before, with single-threaded CPU-
> > bound tasks running almost exclusively on E cores.
> > 
> > Ramses
> 
> I suspect that you may have other issues. I wonder if CPU priorities
> are getting
> assigned properly on your system.
> 
> Saw in the original bugzilla 
> https://bugzilla.kernel.org/show_bug.cgi?id=218195
> that you don't see /proc/sys/kernel/sched_itmt_enabled which
> may be a symptom of such a problem.
> 
> +Srinivas, is there something Ramses can do to help
> find out if there are issues with cppc?
I have updated the bugzilla with the findings. The ACPI config on this
system is telling us that CPPC v2 is not supported. Current
implementation depends on CPPC v2.

Even in 6.4 kernel, ITMT is not enabled.

Thanks,
Srinivas


> 
> Tim
>