From: Andreas Herrmann <aherrmann@suse.com>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <frederic@kernel.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
Linux PM <linux-pm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Commit 554c8aa8ecad causing severe performance degression with pcc-cpufreq
Date: Tue, 17 Jul 2018 12:18:05 +0200 [thread overview]
Message-ID: <20180717101805.ctr3u3vy4gciggw3@suselix> (raw)
In-Reply-To: <20180717093620.ym6phfmr3rfvsxyo@suselix>
On Tue, Jul 17, 2018 at 11:36:20AM +0200, Andreas Herrmann wrote:
> On Tue, Jul 17, 2018 at 11:27:21AM +0200, Andreas Herrmann wrote:
> > On Tue, Jul 17, 2018 at 11:23:25AM +0200, Rafael J. Wysocki wrote:
> > > On Tue, Jul 17, 2018 at 11:11 AM, Andreas Herrmann <aherrmann@suse.com> wrote:
> > > > On Tue, Jul 17, 2018 at 11:06:29AM +0200, Rafael J. Wysocki wrote:
> > > >> On Tue, Jul 17, 2018 at 10:50 AM, Andreas Herrmann <aherrmann@suse.com> wrote:
> > > >>
> > > >> [cut]
> > > >>
> > > >> >
> > > >> > On balance before this commit users could use pcc-cpufreq but had
> > > >> > already suboptimal performance (compared to say intel_pstate driver
> > > >> > which can be used changing BIOS options).
> > > >>
> > > >> BTW, I wonder why you need to change the BIOS options for intel_pstate to load.
> > > >
> > > > I think this is because of (in intel_pstate_init()):
> > > >
> > > > /*
> > > > * The Intel pstate driver will be ignored if the platform
> > > > * firmware has its own power management modes.
> > > > */
> > > > if (intel_pstate_platform_pwr_mgmt_exists())
> > > > return -ENODEV;
> > > >
> > >
> > > OK, because of the "Proliant" entry, right?
> > >
> > > So it looks like we have an issue there. We find the entry and we
> > > look for _PSS. It is not there, so we assume that the firmware is
> > > expected to control performance, which is not the case.
> FYI, there is another BIOS setting on those systems. It's called
> "Collaborative Power Control" (AFAIK enabled by default).
>
> Only if this is disabled, firmware is (alone) in control of
> performance. (And of course in this case neither pcc-cpufreq nor
> intel_pstate will be loaded).
To clarify:
(i) When "Dynamic Power Savings Mode" is enabled _PSS objects are
missing (in fact they seem to be renamed to "XPSS").
pcc-cpufreq driver evaluates PCCH header and loads.
Same when "Collaborative Power Control" is disabled. No _PSS but
XPSS objects. pcc-cpufreq driver fails to evaluate PCCH header,
no cpufreq driver is loaded.
(ii) There are _PSS objects when "OS Control Mode" is selected.
(But I think when "Collaborative Power Control" is disabled there
are no _PSS objects either and the "OS Control Mode" selection
does not matter.)
> > > It looks like we also should look for the presence of the PCC
> > > interface in there.
> > >
> > > I can provide a patch for that, will you be able to test it?
> >
> > Yes, I can test it.
> >
> > > >> It should be initialized before pcc-cpufreq (according to their
> > > >> respective initcall levels), so in theory intel_pstate should be used
> > > >> by default on the affected systems anyway.
> > > >
> > > >> What BIOS settings need to be changed for that?
> > > >
> > > > Already answered in other mail.
> > >
> > > Indeed.
> >
> >
> > Andreas
> >
next prev parent reply other threads:[~2018-07-17 10:18 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-17 6:50 Commit 554c8aa8ecad causing severe performance degression with pcc-cpufreq Andreas Herrmann
2018-07-17 7:33 ` Rafael J. Wysocki
2018-07-17 8:03 ` Rafael J. Wysocki
2018-07-17 8:50 ` Andreas Herrmann
2018-07-17 8:58 ` Rafael J. Wysocki
2018-07-17 9:06 ` Rafael J. Wysocki
2018-07-17 9:11 ` Andreas Herrmann
2018-07-17 9:23 ` Rafael J. Wysocki
2018-07-17 9:27 ` Andreas Herrmann
2018-07-17 9:36 ` Andreas Herrmann
2018-07-17 10:09 ` Rafael J. Wysocki
2018-07-17 10:21 ` Andreas Herrmann
2018-07-17 10:23 ` Rafael J. Wysocki
2018-07-17 14:03 ` Andreas Herrmann
2018-07-17 15:29 ` Rafael J. Wysocki
2018-07-17 16:13 ` [PATCH] cpufreq: intel_pstate: Load when ACPI PCCH is present Rafael J. Wysocki
2018-07-17 17:23 ` Srinivas Pandruvada
2018-07-17 17:28 ` Rafael J. Wysocki
2018-07-17 18:06 ` [PATCH] cpufreq: intel_pstate: Register " Rafael J. Wysocki
2018-07-18 10:43 ` Andreas Herrmann
2018-07-18 10:51 ` Rafael J. Wysocki
2018-07-17 10:18 ` Andreas Herrmann [this message]
2018-07-17 8:08 ` Commit 554c8aa8ecad causing severe performance degression with pcc-cpufreq Daniel Lezcano
2018-07-17 8:36 ` Andreas Herrmann
2018-07-17 8:52 ` Rafael J. Wysocki
2018-07-17 8:15 ` Peter Zijlstra
2018-07-17 9:05 ` Andreas Herrmann
2018-07-17 12:02 ` [PATCH] cpufreq: pcc-cpufreq: Disable dynamic scaling on many-CPU systems Rafael J. Wysocki
2018-07-17 16:14 ` [PATCH v2] " Rafael J. Wysocki
2018-07-17 20:13 ` Andreas Herrmann
2018-07-18 7:44 ` Rafael J. Wysocki
2018-07-18 8:23 ` Peter Zijlstra
2018-07-18 9:34 ` Andreas Herrmann
2018-07-18 15:25 ` Commit 554c8aa8ecad causing severe performance degression with pcc-cpufreq Andreas Herrmann
2018-07-18 15:31 ` Andreas Herrmann
2018-07-19 11:04 ` Andreas Herrmann
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