[Intel-gfx] [PATCH v6 3/3] drm/i915: Predictive governor to control slice/subslice/eu

[Tvrtko Ursulin]

On 26/11/2019 11:31, Tvrtko Ursulin wrote:
> On 26/11/2019 11:09, Chris Wilson wrote:
>> Quoting Tvrtko Ursulin (2019-11-26 10:51:22)
>>> You mentioned you did some experiment where you did something on context
>>> pinning and that it did not work so well. I don't know what that was
>>> though. I don't think that was ever posted?
>>>
>>> What I am thinking is this: You drop the timer altogether. Instead in
>>> __execlists_update_reg_state you look at your gem_context->req_cnt and
>>> implement your logic there.
>>
>> I noticed the same non-sequitur. Except I would push that either the
>> entire measurement and hence patch series is bogus (beyond the patches
>> themselves being trivially broken, tested much?), or that it really
>> should be done from a timer and also adjust pinned contexts ala
>> reconfigure_sseu.
> 
> Yeah, if doing it at pin time would not show the power benefit that 
> would mean looking at req_cnt at pin time does not work, while looking 
> at it half a timer period ago, on average, works. Which would be very 
> intriguing. We'd probably want nice graphs in this case overlaying 
> power, request counts, selected EU config, etc.

Another thing to try, if simple bucketing of req_cnt to load level at 
pin time will not work, could be a time-weighted moving average of the 
same count, but also driven from context pinning.

Regards,

Tvrtko