linux-kernel - Re: [PATCH v1 2/6] cpufreq: intel_pstate: Do not update global.turbo

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Date: Sat, 01 Jun 2024 21:03:18 -0700
From: srinivas pandruvada <srinivas.pandruvada@...ux.intel.com>
To: Xi Ruoyao <xry111@...111.site>, "Rafael J. Wysocki" <rjw@...ysocki.net>,
  Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 2/6] cpufreq: intel_pstate: Do not update
 global.turbo_disabled after initialization

Hi Xi,

On Sun, 2024-06-02 at 11:21 +0800, Xi Ruoyao wrote:
> On Mon, 2024-03-25 at 18:02 +0100, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > 
> > The global.turbo_disabled is updated quite often, especially in the
> > passive mode in which case it is updated every time the scheduler
> > calls
> > into the driver.  However, this is generally not necessary and it
> > adds
> > MSR read overhead to scheduler code paths (and that particular MSR
> > is
> > slow to read).
> > 
> > For this reason, make the driver read
> > MSR_IA32_MISC_ENABLE_TURBO_DISABLE
> > just once at the cpufreq driver registration time and remove all of
> > the
> > in-flight updates of global.turbo_disabled.
> 
> Hi Rafael and Srinivas,
> 
> Thanks for the clean up, but unfortunately on one of my laptops
> (based
> on i5-11300H) MSR_IA32_MISC_ENABLE_TURBO_DISABLE is mysteriously
> changing from 1 to 0 in about one minute after system boot.  I've no
> idea why this is happening (firmware is doing some stupid thing?)
> 
> I've noticed the issue before and "hacked it around"
> (https://bugzilla.kernel.org/show_bug.cgi?id=218702). But after this
> change I can no longer hack it around and the system is much slower.
> 
> Is it possible to hack it around again?
> 
Please try the attached diff and build kernel and try.

git apply update_max_freq.diff

Then build kernel and install.

Thanks,
Srinivas

View attachment "update_max_freq.diff" of type "text/x-patch" (578 bytes)