linux-kernel - Re: [PATCH 4/4] cpufreq: intel_pstate: enable boost for Skylake Xeon

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:   Tue, 31 Jul 2018 17:04:38 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     Eero Tamminen <eero.t.tamminen@...el.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Francisco Jerez <currojerez@...eup.net>, lenb@...nel.org,
        rjw@...ysocki.net, ggherdovich@...e.cz, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, juri.lelli@...hat.com,
        viresh.kumar@...aro.org, Chris Wilson <chris@...is-wilson.co.uk>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
Subject: Re: [PATCH 4/4] cpufreq: intel_pstate: enable boost for Skylake Xeon

On Mon, Jul 30, 2018 at 07:06:21AM -0700, Srinivas Pandruvada wrote:
> On Mon, 2018-07-30 at 14:16 +0300, Eero Tamminen wrote:
> > Questions:
> > 
> > * Does currently kernel CPU freq management have any idea which IO
> >    devices share TDP with the CPU cores?

> No. The requests we do to hardware is just indication only (HW can
> ignore it). The HW has a bias register to adjust and distribute power
> among users.
> We can have several other active device on servers beside CPU which
> when runs need extra power. So the HW arbitrates power.

That's not entirely accurate AFAIK. "No" is accurate for Intel, but the
ARM people have their IPA thing (not a beer):

  https://developer.arm.com/open-source/intelligent-power-allocation

  drivers/thermal/power_allocator.c

which IIUC interacts with their cpufreq driver to disallow certain OPP
states.

And note that I discourage intel_pstate active mode.