Re: [PATCH 09/15] x86, amd: add accessor for number of cores per compute unit

Guenter Roeck
2015-08-31T16:19:28Z

On 08/31/2015 09:06 AM, Borislav Petkov wrote:
> On Mon, Aug 31, 2015 at 10:38:21AM +0200, Peter Zijlstra wrote:
>> Looking at the BKDG Fam 15h 60h-6Fh these MSRs are per compute unit.
>> This means you can do much finer grained measurements than system wide
>
> Well, we can do finer-grained if needed. I'm all for everything which
> has a good use case. The use case we had in mind here was the physical
> processor power consumption for a time period.
>
>> -- which is all hwmon seems capable of.
>
> I guess we can do both - perf and hwmon. I don't see why not.
>
>> Not to mention the proposed code is horrible, who in their right mind
>> does two rdmsrl_safe_on_cpu() back to back.
>
> That's a good point - I missed that during previous review. Rui, please
> put the rdmsrl_safe_on_cpu() accesses in a separate function which you
> run on a particular CPU, for your next version.
>
... and maybe work with Peter to address the other hotplug related issues.

It might also be worthwhile thinking about per-CU attributes, if that
provides any value (Peter's comments suggested that this might be the case).

Thanks,
Guenter