Re: [PATCH] [RFC] ondemand governor: dynamic cpufreq scaling withdifferent CPUs
From: Venki Pallipadi
Date: Wed Aug 10 2011 - 12:59:39 EST
On Mon, Aug 1, 2011 at 7:51 AM, Len Brown <lenb@xxxxxxxxxx> wrote:
> Re: software vs hardware coordination
> Speaking for Intel, everything we make, from hand-sets to supercomputers
> supports hardware coorination.
> Think about it -- if we did not, then we would not be able
> to support a legacy OS that doesn't know how to do SW coordination.
> HW coordiation is the simplest thing for the SW because
> SW doesn't have to know anything at all about topology constraints.
> It is also the simplest thing for the BIOS, which doesn't have
> to correctly describe topology.
> Yes, there is an MSR bit that the BIOS can flip to disable
> HW coordination. 90% of the time that bit is set it is a BIOS bug.
> eg. the bit is set, but the BIOS fails to properly set up the
> ACPI tables to properly enable SW coordination, resulting
> in a system with really strange performance issues.
> Indeed, I proposed before, and I will propose again that
> the underlying ACPI _PSD support behind SW coordination
> be completely removed from Linux.
> I recall that you mentioned one platform that depends on it --
> and I'd like to understand that issue and address it with a quirk
> rather than expose all systems to BIOS bugs due to bogus _PSD support.
Agree. Addressing this as a quirk would be fine. The processor that
needs it is E74xx series, IIRC.
> Your system is running in SW coordination mode?
> What do you see if you run with the patch below?
> I'd be intersted to see the output from adpidump for your system.
> -Len Brown
> Intel Open Source Technology Center
> diff --git a/include/acpi/pdc_intel.h b/include/acpi/pdc_intel.h
> index 552637b..d081595 100644
> --- a/include/acpi/pdc_intel.h
> +++ b/include/acpi/pdc_intel.h
> @@ -22,7 +22,6 @@
> #define ACPI_PDC_EST_CAPABILITY_SWSMP (ACPI_PDC_SMP_C1PT | \
> ACPI_PDC_C_C1_HALT | \
> - ACPI_PDC_SMP_P_SWCOORD | \
> ACPI_PDC_SMP_P_HWCOORD | \
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