From: Andreas Herrmann <aherrmann@suse.com>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
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 16:03:36 +0200 [thread overview]
Message-ID: <20180717140336.ayovaz4ksdlak6bb@suselix> (raw)
In-Reply-To: <20180717102136.snayvzmv2h3dcwiq@suselix>
On Tue, Jul 17, 2018 at 12:21:36PM +0200, Andreas Herrmann wrote:
> On Tue, Jul 17, 2018 at 12:09:21PM +0200, Rafael J. Wysocki wrote:
---8<---
> > OK, the patch is below.
> >
> > First, I hope that if "Collaborative Power Control" is disabled, it will
> > simply hide the PCCH object and so intel_pstate will still not load then.
>
> PCCH is hidden in that case.
>
> > The main question basically is what the OS is expected to do if
> > "Dynamic Power Savings Mode" is set. If we are *expected* to use
> > the PCC interface then, intel_pstate may not work in that case, but
> > I suspect that the PCC interface allows extra energy to be saved
> > over what is possible without it.
>
> I'll test it and see what happens.
I've tested it on top of v4.18-rc5-36-g30b06abfb92b. intel_pstate now
loads instead of pcc-cpufreq and system looks stable.
When disabling "Collaborative Power Control" no cpufreq driver is loaded
(as expected).
Performance (with kernbench) is as expected (always better than any
brew of pcc-cpufreq + misc modifications to this driver + partial
rollback of commit 554c8aa8ecad).
If you like you can add either Tested-by or
Reviewed-by: Andreas Herrmann <aherrmann@suse.com>
I think this patch should be tagged for 4.17-stable.
Thanks,
Andreas
> > ---
> > drivers/cpufreq/intel_pstate.c | 17 ++++++++++++++++-
> > 1 file changed, 16 insertions(+), 1 deletion(-)
> >
> > Index: linux-pm/drivers/cpufreq/intel_pstate.c
> > ===================================================================
> > --- linux-pm.orig/drivers/cpufreq/intel_pstate.c
> > +++ linux-pm/drivers/cpufreq/intel_pstate.c
> > @@ -2391,6 +2391,18 @@ static bool __init intel_pstate_no_acpi_
> > return true;
> > }
> >
> > +static bool __init intel_pstate_no_acpi_pcch(void)
> > +{
> > + acpi_status status;
> > + acpi_handle handle;
> > +
> > + status = acpi_get_handle(NULL, "\\_SB", &handle);
> > + if (ACPI_FAILURE(status))
> > + return true;
> > +
> > + return !acpi_has_method(handle, "PCCH");
> > +}
> > +
> > static bool __init intel_pstate_has_acpi_ppc(void)
> > {
> > int i;
> > @@ -2450,7 +2462,10 @@ static bool __init intel_pstate_platform
> >
> > switch (plat_info[idx].data) {
> > case PSS:
> > - return intel_pstate_no_acpi_pss();
> > + if (!intel_pstate_no_acpi_pss())
> > + return false;
> > +
> > + return intel_pstate_no_acpi_pcch();
> > case PPC:
> > return intel_pstate_has_acpi_ppc() && !force_load;
> > }
> >
> >
next prev parent reply other threads:[~2018-07-17 14:04 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 [this message]
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 ` Commit 554c8aa8ecad causing severe performance degression with pcc-cpufreq Andreas Herrmann
2018-07-17 8:08 ` 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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