[Intel-gfx] [PATCH v2] drm/i915: Reduce i915_request_alloc retirement to local context

[Tvrtko Ursulin]

On 09/01/2019 13:14, Chris Wilson wrote:
> In the continual quest to reduce the amount of global work required when
> submitting requests, replace i915_retire_requests() after allocation
> failure to retiring just our ring.
> 
> v2: Don't forget the list iteration included an early break, so we would
> never throttle on the last request in the ring/timeline.
> 
> References: 11abf0c5a021 ("drm/i915: Limit the backpressure for i915_request allocation")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> ---
>   drivers/gpu/drm/i915/i915_request.c | 35 +++++++++++++++++++++--------
>   1 file changed, 26 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> index 1e158eb8cb97..e183009f47f4 100644
> --- a/drivers/gpu/drm/i915/i915_request.c
> +++ b/drivers/gpu/drm/i915/i915_request.c
> @@ -477,6 +477,31 @@ submit_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state)
>   	return NOTIFY_DONE;
>   }
>   
> +static noinline struct i915_request *
> +i915_request_alloc_slow(struct intel_context *ce)
> +{
> +	struct intel_ring *ring = ce->ring;
> +	struct i915_request *rq, *next;
> +
> +	if (list_empty(&ring->request_list))
> +		goto out;
> +
> +	/* Ratelimit ourselves to prevent oom from malicious clients */
> +	rq = list_last_entry(&ring->request_list, typeof(*rq), ring_link);
> +	cond_synchronize_rcu(rq->rcustate);
> +
> +	/* Retire our old requests in the hope that we free some */
> +	list_for_each_entry_safe(rq, next, &ring->request_list, ring_link) {
> +		if (!i915_request_completed(rq))
> +			break;
> +
> +		i915_request_retire(rq);
> +	}

Now this is more similar to ring_retire_requests. ;)

> +
> +out:
> +	return kmem_cache_alloc(ce->gem_context->i915->requests, GFP_KERNEL);
> +}
> +
>   /**
>    * i915_request_alloc - allocate a request structure
>    *
> @@ -559,15 +584,7 @@ i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx)
>   	rq = kmem_cache_alloc(i915->requests,
>   			      GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
>   	if (unlikely(!rq)) {
> -		i915_retire_requests(i915);
> -
> -		/* Ratelimit ourselves to prevent oom from malicious clients */
> -		rq = i915_gem_active_raw(&ce->ring->timeline->last_request,
> -					 &i915->drm.struct_mutex);
> -		if (rq)
> -			cond_synchronize_rcu(rq->rcustate);
> -
> -		rq = kmem_cache_alloc(i915->requests, GFP_KERNEL);
> +		rq = i915_request_alloc_slow(ce);
>   		if (!rq) {
>   			ret = -ENOMEM;
>   			goto err_unreserve;
> 

With the retire consolidated:

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

Regards,

Tvrtko