linux-kernel - Re: [PATCH v4 10/10] cpufreq: intel_pstate: Use CPPC to get max performance

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Message-ID: <alpine.DEB.2.20.1609222055110.5640@nanos>
Date:   Thu, 22 Sep 2016 20:56:02 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...e.de>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>, jolsa@...hat.com
Subject: Re: [PATCH v4 10/10] cpufreq: intel_pstate: Use CPPC to get max
 performance

On Thu, 22 Sep 2016, Tim Chen wrote:
> On Wed, 2016-09-21 at 22:30 +0200, Rafael J. Wysocki wrote:
> > My current understanding is that we need to rebuild sched domains
> > after setting the priorities, 
> 
> No, that's not true.  We need to rebuild the sched domains only
> when the sched domain flags are changed, not when we are changing
> the priorities.  Only the sched domain flag is a property of
> the sched domain. CPU priority values are not part of sched domain.
> 
> Morten had similar question about whether we need to rebuild sched domain
> when we change cpu priorities when we first post the patches. 
> Peter has explained that it wasn't necessary.
> http://lkml.iu.edu/hypermail/linux/kernel/1608.3/01753.html

And why is there no explanation in form of a comment in the code?

Thanks,

	tglx