Re: [PATCH 2/2 V8] intel_pstate: add kernel parameter to force loading.
From: Rafael J. Wysocki
Date: Fri Dec 05 2014 - 17:07:17 EST
On Friday, December 05, 2014 11:09:29 AM Linda Knippers wrote:
> On 12/5/2014 4:40 AM, Ethan Zhao wrote:
> > To force loading on Oracle Sun X86 servers, provide one kernel command line
> > parameter
> > intel_pstate = force
> > For those who be aware of the risk of no power capping capabily working and
> > try to get better performance with this driver.
> > Signed-off-by: Ethan Zhao <ethan.zhao@xxxxxxxxxx>
> > Tested-by: Alexey Kodanev <alexey.kodanev@xxxxxxxxxx>
> > ---
> > v2: change to hardware vendor specific naming parameter.
> > v4: refine code and doc.
> > v5&v6: fix a typo in doc.
> > v7: change enum PCC to PPC.
> > v8: change the name of kernel command line parameter to generic one.
> > Documentation/kernel-parameters.txt | 5 +++++
> > drivers/cpufreq/intel_pstate.c | 6 +++++-
> > 2 files changed, 10 insertions(+), 1 deletion(-)
> > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> > index 479f332..7d0983e 100644
> > --- a/Documentation/kernel-parameters.txt
> > +++ b/Documentation/kernel-parameters.txt
> > @@ -1446,6 +1446,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> > disable
> > Do not enable intel_pstate as the default
> > scaling driver for the supported processors
> > + force
> > + Enable intel_pstate on systems where it may cause problems to
> > + happen due to conflicts with platform firmware attempting to
> > + drive P-states by itself in certain situations (for thermal
> > + control or power capping in general or other purposes).
> I suggest something like:
> Enable intel_pstate on systems that prohibit it by
> default in favor of acpi-cpufreq. Forcing the
> intel_pstate driver instead of acpi-cpufreq may disable
> platform features, such as thermal controls and power
> capping, that rely on ACPI p-state information being
> used by the OS and therefore should be used with care.
> This option does not work with processors that aren't
> supported by the intel_pstate driver or on platforms
> that use pcc-cpufreq instead of acpi-cpufreq.
> Maybe this is too specific but I believe it is accurate. Comments?
Looks good to me, thanks!
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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