[Intel-gfx] [PATCH v2 3/3] drm/i915/perf: enable filtering on multiple contexts

[Lionel Landwerlin]

On 06/04/2020 17:27, Chris Wilson wrote:
> Quoting Lionel Landwerlin (2020-04-06 15:07:30)
>> On 06/04/2020 16:59, Chris Wilson wrote:
>>> Quoting Lionel Landwerlin (2020-04-06 14:54:38)
>>>> On 31/03/2020 21:08, Chris Wilson wrote:
>>>>> Quoting Lionel Landwerlin (2020-03-31 12:48:21)
>>>>>> Add 2 new properties to the i915-perf open ioctl to specify an array
>>>>>> of GEM context handles as well as the length of the array.
>>>>> Hmm. The other thought is ctx->engine[] where one context may have more
>>>>> than one logical context instance that OA could track. The extension to
>>>>> track multiple pinned contexts should equally work for multiple engines.
>>>>>
>>>>>         I915_DEFINE_CONTEXT_PARAM_ENGINES(engines, 64) = {};
>>>>>         struct drm_i915_gem_context_param p = {
>>>>>                 .ctx_id = gem_context_create(i915),
>>>>>                 .param = I915_CONTEXT_PARAM_ENGINES,
>>>>>                 .value = to_user_pointer(&engines),
>>>>>                 .size = sizeof(struct i915_context_param_engines),
>>>>>         };
>>>>>         gem_context_set_param(i915, &p);
>>>>>
>>>>> would do the trick in creating one context with 64 rcs0 that they may
>>>>> want to track. And that also opens the door to virtual engines over top.
>>>>> -Chris
>>>> I rather punt this away for now :)
>>>>
>>>> I can't see use cases for Iris/Vulkan.
>>> There's immediate use cases for iris, since it uses 2 contexts instead
>>> of 2 logical instances within one GL/GEM context.
>>
>> I don't understand this. Are you saying Iris could use the stuff from
>> above and still select what logical context to dispatch to?
> Yes. And can be done so only by changing the context setup to create one
> context with two independent rcs engines (different logical GPU state,
> and rings, *only* sharing the same vm). And since legacy EXEC_DEFAULT[0]
> and EXEC_RENDER[1] alias to the same engine, very little code needs to be
> changed to support (1 ctx, 2 engines) vs (2 ctx, 1 engine).
> -Chris

Sounds like there could a performance gain somewhere...

Will look into this.


-Lionel