linux-kernel - Re: [PATCH v7] cpufreq: intel_pstate: Implement passive mode with HWP enabled

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 11 Aug 2020 17:33:49 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Francisco Jerez <currojerez@...eup.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Linux Documentation <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        Doug Smythies <dsmythies@...us.net>,
        Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH v7] cpufreq: intel_pstate: Implement passive mode with HWP enabled

On Tuesday, August 11, 2020 2:51:41 AM CEST Francisco Jerez wrote:
> 
> --==-=-=
> Content-Type: multipart/mixed; boundary="=-=-="
> 
> --=-=-=
> Content-Type: text/plain; charset=utf-8
> Content-Disposition: inline
> Content-Transfer-Encoding: quoted-printable
> 
> "Rafael J. Wysocki" <rjw@...ysocki.net> writes:
> 
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > Allow intel_pstate to work in the passive mode with HWP enabled and
> > make it set the HWP minimum performance limit (HWP floor) to the
> > P-state value given by the target frequency supplied by the cpufreq
> > governor, so as to prevent the HWP algorithm and the CPU scheduler
> > from working against each other, at least when the schedutil governor
> > is in use, and update the intel_pstate documentation accordingly.
> >
> > Among other things, this allows utilization clamps to be taken
> > into account, at least to a certain extent, when intel_pstate is
> > in use and makes it more likely that sufficient capacity for
> > deadline tasks will be provided.
> >
> > After this change, the resulting behavior of an HWP system with
> > intel_pstate in the passive mode should be close to the behavior
> > of the analogous non-HWP system with intel_pstate in the passive
> > mode, except that in the frequency range below the base frequency
> > (ie. the frequency retured by the base_frequency cpufreq attribute
> > in sysfs on HWP systems) the HWP algorithm is allowed to make the
> > CPU run at a frequency above the floor P-state set by intel_pstate,
> > with or without hardware coordination of P-states among CPUs in the
> > same package.
> >
> 
> The "frequency range below the base frequency" part of the paragraph
> above seems somewhat misleading, since AFAICT the same thing will happen
> in the P-state range above the base frequency. 

Fair enough.  I rephrased the changelog when applying the patch.

> Another minor comment below, other than that LGTM:

And this one has been fixed too.

> Reviewed-by: Francisco Jerez <currojerez@...eup.net>

Thanks!