Re: [Intel-gfx] [PATCH] drm/i915/pmu: "Frequency" is reported as accumulated cycles

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 11/11/2019 09:43, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2019-11-11 09:11:03)
>>
>> On 09/11/2019 10:53, Chris Wilson wrote:
>>> We report "frequencies" (actual-frequency, requested-frequency) as the
>>> number of accumulated cycles so that the average frequency over that
>>> period may be determined by the user. This means the units we report to
>>> the user are Mcycles (or just M), not MHz.
>>>
>>> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
>>> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>> Cc: stable@vger.kernel.org
>>> ---
>>>    drivers/gpu/drm/i915/i915_pmu.c | 4 ++--
>>>    1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
>>> index 4804775644bf..9b02be0ad4e6 100644
>>> --- a/drivers/gpu/drm/i915/i915_pmu.c
>>> +++ b/drivers/gpu/drm/i915/i915_pmu.c
>>> @@ -908,8 +908,8 @@ create_event_attributes(struct i915_pmu *pmu)
>>>                const char *name;
>>>                const char *unit;
>>>        } events[] = {
>>> -             __event(I915_PMU_ACTUAL_FREQUENCY, "actual-frequency", "MHz"),
>>> -             __event(I915_PMU_REQUESTED_FREQUENCY, "requested-frequency", "MHz"),
>>> +             __event(I915_PMU_ACTUAL_FREQUENCY, "actual-frequency", "M"),
>>> +             __event(I915_PMU_REQUESTED_FREQUENCY, "requested-frequency", "M"),
>>>                __event(I915_PMU_INTERRUPTS, "interrupts", NULL),
>>>                __event(I915_PMU_RC6_RESIDENCY, "rc6-residency", "ns"),
>>>        };
>>>
>>
>> MHz was wrong yes. But is 'M' established or would 'Mcycles' be better?
> 
> The only place where "cycles" pops up is in the perf ui, the other
> events that I thought were similar in nature are unitless. As the
> 'cycle' itself is not an SI base unit as it is a mere count.
> 
> ~o~ I have no idea ~o~

But if the argument if that 'cycle' is not SI then neither is 'M'. So I 
think I would prefer 'Mcycles'. Nevertheless, I guess a strange 'M' is 
better than wrong 'MHz'.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko