Re: [Intel-gfx] [PATCH 22/25] drm/i915: Make request conflict tracking understand parallel submits

[John Harrison <john.c.harrison@intel.com>]

On 10/13/2021 13:42, Matthew Brost wrote:
> If an object in the excl or shared slot is a composite fence from a
> parallel submit and the current request in the conflict tracking is from
> the same parallel context there is no need to enforce ordering as the
> ordering is already implicit. Make the request conflict tracking
> understand this by comparing a parallel submit's parent context and
> skipping conflict insertion if the values match.
>
> v2:
>   (John Harrison)
>    - Reword commit message
>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>

> ---
>   drivers/gpu/drm/i915/i915_request.c | 43 +++++++++++++++++++----------
>   1 file changed, 29 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> index 8bdf9f2f9b90..820a1f38b271 100644
> --- a/drivers/gpu/drm/i915/i915_request.c
> +++ b/drivers/gpu/drm/i915/i915_request.c
> @@ -1335,6 +1335,25 @@ i915_request_await_external(struct i915_request *rq, struct dma_fence *fence)
>   	return err;
>   }
>   
> +static inline bool is_parallel_rq(struct i915_request *rq)
> +{
> +	return intel_context_is_parallel(rq->context);
> +}
> +
> +static inline struct intel_context *request_to_parent(struct i915_request *rq)
> +{
> +	return intel_context_to_parent(rq->context);
> +}
> +
> +static bool is_same_parallel_context(struct i915_request *to,
> +				     struct i915_request *from)
> +{
> +	if (is_parallel_rq(to))
> +		return request_to_parent(to) == request_to_parent(from);
> +
> +	return false;
> +}
> +
>   int
>   i915_request_await_execution(struct i915_request *rq,
>   			     struct dma_fence *fence)
> @@ -1366,11 +1385,14 @@ i915_request_await_execution(struct i915_request *rq,
>   		 * want to run our callback in all cases.
>   		 */
>   
> -		if (dma_fence_is_i915(fence))
> +		if (dma_fence_is_i915(fence)) {
> +			if (is_same_parallel_context(rq, to_request(fence)))
> +				continue;
>   			ret = __i915_request_await_execution(rq,
>   							     to_request(fence));
> -		else
> +		} else {
>   			ret = i915_request_await_external(rq, fence);
> +		}
>   		if (ret < 0)
>   			return ret;
>   	} while (--nchild);
> @@ -1471,10 +1493,13 @@ i915_request_await_dma_fence(struct i915_request *rq, struct dma_fence *fence)
>   						 fence))
>   			continue;
>   
> -		if (dma_fence_is_i915(fence))
> +		if (dma_fence_is_i915(fence)) {
> +			if (is_same_parallel_context(rq, to_request(fence)))
> +				continue;
>   			ret = i915_request_await_request(rq, to_request(fence));
> -		else
> +		} else {
>   			ret = i915_request_await_external(rq, fence);
> +		}
>   		if (ret < 0)
>   			return ret;
>   
> @@ -1525,16 +1550,6 @@ i915_request_await_object(struct i915_request *to,
>   	return ret;
>   }
>   
> -static inline bool is_parallel_rq(struct i915_request *rq)
> -{
> -	return intel_context_is_parallel(rq->context);
> -}
> -
> -static inline struct intel_context *request_to_parent(struct i915_request *rq)
> -{
> -	return intel_context_to_parent(rq->context);
> -}
> -
>   static struct i915_request *
>   __i915_request_ensure_parallel_ordering(struct i915_request *rq,
>   					struct intel_timeline *timeline)