Re: [Xen-devel] [PATCH v2] x86: Use deep C states for off-lined CPUs

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.03.12 at 18:01, Boris Ostrovsky <boris.ostrovsky@xxxxxxx> wrote:
> Jan was objecting to moving it in this patch because it is not directly 
> related to the functionality that the patch was addressing. Or was it 
> because it wasn't properly done?

And similarly Jinsong suggested to do this in _another_ patch.

Jan

> On 03/04/12 10:09, Liu, Jinsong wrote:
>> Fine to me.
>> BTW, seems another patch moving mwait_ptr declaration and related code into 
> if(FFH) is slightly better? It's FFH staff anyway.
>>
>> Thanks,
>> Jinsong
>>
>> Boris Ostrovsky wrote:
>>> # HG changeset patch
>>> # User Boris Ostrovsky<boris.ostrovsky@xxxxxxx>
>>> # Date 1330642361 -3600
>>> # Node ID 99df5c6b2964ceaa73651d7bc02fb1ae820f7691
>>> # Parent  a7bacdc5449a2f7bb9c35b2a1334b463fe9f29a9
>>> x86: Use deep C states for off-lined CPUs
>>>
>>> Currently when a core is taken off-line it is placed in C1 state
>>> (unless MONITOR/MWAIT is used). This patch allows a core to go to
>>> deeper C states resulting in significantly higher power savings.
>>>
>>> Signed-off-by: Boris Ostrovsky<boris.ostrovsky@xxxxxxx>
>>>
>>> diff -r a7bacdc5449a -r 99df5c6b2964 xen/arch/x86/acpi/cpu_idle.c
>>> --- a/xen/arch/x86/acpi/cpu_idle.c  Mon Feb 27 17:05:18 2012 +0000
>>> +++ b/xen/arch/x86/acpi/cpu_idle.c  Thu Mar 01 23:52:41 2012 +0100
>>> @@ -566,6 +566,7 @@ static void acpi_dead_idle(void)
>>>       struct acpi_processor_power *power;
>>>       struct acpi_processor_cx *cx;
>>>       void *mwait_ptr;
>>> +    struct cpuinfo_x86 *c =&current_cpu_data;
>>>
>>>       if ( (power = processor_powers[smp_processor_id()]) == NULL )
>>>           goto default_halt;
>>> @@ -601,6 +602,23 @@ static void acpi_dead_idle(void)
>>>               mb();
>>>               __mwait(cx->address, 0);
>>>           }
>>> +    }
>>> +    else if ( c->x86_vendor == X86_VENDOR_AMD&&
>>> +              cx->entry_method == ACPI_CSTATE_EM_SYSIO )
>>> +    {
>>> +        /* Intel prefers not to use SYSIO */
>>> +
>>> +        /* Avoid references to shared data after the cache flush */
>>> +        u32 address = cx->address;
>>> +        u32 pmtmr_ioport_local = pmtmr_ioport;
>>> +
>>> +        wbinvd();
>>> +
>>> +        while ( 1 )
>>> +        {
>>> +            inb(address);
>>> +            inl(pmtmr_ioport_local);
>>> +        }
>>>       }
>>>
>>>   default_halt:
>>
>>




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