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

Guenter Roeck
2015-08-31T13:54:06Z

On 08/31/2015 06:38 AM, Peter Zijlstra wrote:
> On Mon, Aug 31, 2015 at 06:26:00AM -0700, Guenter Roeck wrote:
>> On 08/31/2015 01:38 AM, Peter Zijlstra wrote:
>>> On Sun, Aug 30, 2015 at 05:53:22PM +0200, Borislav Petkov wrote:
>>>> On Sat, Aug 29, 2015 at 11:19:14AM +0200, Ingo Molnar wrote:
>>>>> So let me withdraw my ack: the much more important question that I
>>>>> missed first time around, why is this reporting feature living in
>>>>> hwmon, not in perf? We have energy reporting facilities in perf that
>>>>> this should be synced to.
>>>>
>>>> Because there's already fam15h_power driver which is exactly for that.
>>>> Making it part of perf is then a question of cat-ting the same sysfs
>>>> file twice, at the beginning and at the end of the trace, which is
>>>> trivial.
>>>
>>> That don't make sense.
>>>
>>> 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
>>> -- which is all hwmon seems capable of.
>>>
>>
>> Is it ? Why ?
>
> Dunno, because there's that big old loop iterating all cpus?
>

What does that have to do with 'hwmon' ? The current implementation in the
driver may not be a good idea, and maybe for good reasons; I can not
comment on that. However, you concluded from that implementation that
hwmon, the subsystem, would not be able to support 'much finer grained
measurements than system wide'. I would like to understand how you reached
that conclusion.

Thanks,
Guenter