Re: [Xen-devel] [PATCH] AMD, powernow: Update P-state directly when _PSD's CoordType is DOMAIN_COORD_TYPE_HW_ALL

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.08.12 at 15:50, Boris Ostrovsky <boris.ostrovsky@xxxxxxx> wrote:
> On 08/17/2012 06:31 AM, Jan Beulich wrote:
>>>>> On 16.08.12 at 18:41, Boris Ostrovsky <boris.ostrovsky@xxxxxxx> wrote:
>>> @@ -137,26 +122,28 @@ static int powernow_cpufreq_target(struc
>>>               return 0;
>>>       }
>>>
>>> -    if (policy->shared_type != CPUFREQ_SHARED_TYPE_ANY)
>>> -        cmd.mask = &online_policy_cpus;
>>> -    else
>>> -        cmd.mask = cpumask_of(policy->cpu);
>>> +    if (policy->shared_type == CPUFREQ_SHARED_TYPE_HW &&
>>> +        likely(policy->cpu == smp_processor_id())) {
>>> +        transition_pstate(&next_perf_state);
>>> +        cpufreq_statistic_update(policy->cpu, perf->state, 
>>> next_perf_state);
>>
>> Actually - is this enough? Doesn't this also need to be done based
>> on policy->cpus?
> 
> With HW-coordinated transitions there is a policy structure per CPU so 
> policy->cpus is always 1 and policy->cpu is the same as policy->cpus. 
> You can see this in cpufreq_add_cpu(), when hw_all is set.
> 
> (This is consistent with ACPI spec:
>       When hardware coordinates transitions, OSPM continues to
>       initiate state transitions as it would if there were no
>       dependencies.
> )

Ah, okay, I didn't recall that (which means in this case the stats
simply can't be right, as the hardware may do as it pleases).

Jan


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