Xen devel - Mar 2011 - Re: [RFC PATCH V4 3/5] cpuidle: default idle driver for x86

On 03/23/2011 08:43 AM, Len Brown wrote:
> Why is this patch a step forward?
Hi Len,

I have basically moved the code for arch default and mwait
idle from arch/x86/kernel/process.c to a driver. This was
suggested by Venki (https://lkml.org/lkml/2010/10/19/460)
as part of pm_idle cleanup and direct call of
cpuidle_idle_call(). There is not much new code here.
>
>> +obj-$(CONFIG_X86)                              += default_driver.o
>
> BTW, that''s a pretty generic name for an x86 specific idle
driver...
>
> I think that on builds that support intel_idle and acpi_idle,
> everything in this file will be unused, unless somebody uses some
> debugging cmdline params that should have been deleted ages ago.
Yes, I agree that the name has to be x86 specific. I think the
routines would be used for pre-nehalem architectures that use
arch default or mwait.

Thanks,
-Trinabh
>
> thanks,
> Len Brown, Intel Open Source Technology Center
>
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* Trinabh Gupta <trinabh@linux.vnet.ibm.com> [2011-03-23 15:01:14]:
> 
> On 03/23/2011 08:43 AM, Len Brown wrote:
> >Why is this patch a step forward?
> 
> Hi Len,
> 
> I have basically moved the code for arch default and mwait
> idle from arch/x86/kernel/process.c to a driver. This was
> suggested by Venki (https://lkml.org/lkml/2010/10/19/460)
> as part of pm_idle cleanup and direct call of
> cpuidle_idle_call(). There is not much new code here.
> 
> >
> >>+obj-$(CONFIG_X86)                              += default_driver.o
> >
> >BTW, that''s a pretty generic name for an x86 specific idle
driver...
> >
> >I think that on builds that support intel_idle and acpi_idle,
> >everything in this file will be unused, unless somebody uses some
> >debugging cmdline params that should have been deleted ages ago.
> 
> Yes, I agree that the name has to be x86 specific. I think the
> routines would be used for pre-nehalem architectures that use
> arch default or mwait.
Mainly selection between default_idle (safe_halt), mwait_idle and
c1e_idle needs to be placed in a default driver.  This is the code
that was ''outside'' of cpuidle framework and directly used
pm_idle().
This is mostly unused and overridden by intel_idle or acpi_idle, but
still cannot be discarded.

Maybe keep this as a module and probe/load only if both intel_idle and
acpi_idle failed to load or excluded by command line or otherwise.

--Vaidy


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