[Intel-gfx] [PATCH 4/6] drm/i915/pmu: Add reference counting to the sampling timer

[Dixit, Ashutosh]

On Fri, 05 May 2023 17:58:14 -0700, Umesh Nerlige Ramappa wrote:
>
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>
> We do not want to have timers per tile and waste CPU cycles and energy via
> multiple wake-up sources, for a relatively un-important task of PMU
> sampling, so keeping a single timer works well. But we also do not want
> the first GT which goes idle to turn off the timer.

Apart from this efficiency, what is the reason for having a device level
PMU (which monitors gt level events), rather than independent gt level
PMU's (each of which monitor events from that gt)?

Wouldn't independent gt level PMU's be simpler? And user space tools (say
intel-gpu-top) would hook into events from a gt and treat each gt
independently?

So my question really is what is the reason for keeping the PMU device
level rather than per gt?

Thanks.
--
Ashutosh