Re: [PATCH v2 07/11] drm/i915/scheduler: Boost priorities for flips

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 07/11/2016 13:59, Chris Wilson wrote:
> Boost the priority of any rendering required to show the next pageflip
> as we want to avoid missing the vblank by being delayed by invisible
> workload. We prioritise avoiding jank and jitter in the GUI over
> starving background tasks.
>
> v2: Descend dma_fence_array when boosting priorities.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_drv.h      |  5 +++
>  drivers/gpu/drm/i915/i915_gem.c      | 63 ++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_display.c |  2 ++
>  3 files changed, 70 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index e790147209f3..5c658c6d06e4 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -3420,6 +3420,11 @@ int i915_gem_object_wait(struct drm_i915_gem_object *obj,
>  			 unsigned int flags,
>  			 long timeout,
>  			 struct intel_rps_client *rps);
> +int i915_gem_object_wait_priority(struct drm_i915_gem_object *obj,
> +				  unsigned int flags,
> +				  int priority);
> +#define I915_PRIORITY_DISPLAY I915_PRIORITY_MAX
> +
>  int __must_check
>  i915_gem_object_set_to_gtt_domain(struct drm_i915_gem_object *obj,
>  				  bool write);
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index a4dc2da2323a..ae31686fb16d 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -34,6 +34,7 @@
>  #include "intel_drv.h"
>  #include "intel_frontbuffer.h"
>  #include "intel_mocs.h"
> +#include <linux/dma-fence-array.h>
>  #include <linux/reservation.h>
>  #include <linux/shmem_fs.h>
>  #include <linux/slab.h>
> @@ -433,6 +434,68 @@ i915_gem_object_wait_reservation(struct reservation_object *resv,
>  	return timeout;
>  }
>
> +static void __fence_set_priority(struct dma_fence *fence, int prio)
> +{
> +	struct drm_i915_gem_request *rq;
> +	struct intel_engine_cs *engine;
> +
> +	if (!dma_fence_is_i915(fence))
> +		return;
> +
> +	rq = to_request(fence);
> +	engine = rq->engine;
> +	if (!engine->schedule)
> +		return;
> +
> +	engine->schedule(rq, prio);
> +}
> +
> +static void fence_set_priority(struct dma_fence *fence, int prio)
> +{
> +	if (dma_fence_is_array(fence)) {
> +		struct dma_fence_array *array = to_dma_fence_array(fence);
> +		int i;
> +
> +		for (i = 0; i < array->num_fences; i++)
> +			__fence_set_priority(array->fences[i], prio);
> +	} else
> +		__fence_set_priority(fence, prio);
> +}
> +
> +int
> +i915_gem_object_wait_priority(struct drm_i915_gem_object *obj,
> +			      unsigned int flags,
> +			      int prio)
> +{
> +	struct dma_fence *excl;
> +
> +	if (flags & I915_WAIT_ALL) {
> +		struct dma_fence **shared;
> +		unsigned int count, i;
> +		int ret;
> +
> +		ret = reservation_object_get_fences_rcu(obj->resv,
> +							&excl, &count, &shared);
> +		if (ret)
> +			return ret;
> +
> +		for (i = 0; i < count; i++) {
> +			fence_set_priority(shared[i], prio);
> +			dma_fence_put(shared[i]);
> +		}
> +
> +		kfree(shared);
> +	} else {
> +		excl = reservation_object_get_excl_rcu(obj->resv);
> +	}
> +
> +	if (excl) {
> +		fence_set_priority(excl, prio);
> +		dma_fence_put(excl);
> +	}
> +	return 0;
> +}
> +
>  /**
>   * Waits for rendering to the object to be completed
>   * @obj: i915 gem object
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 92ab01f33208..650e2e452a2c 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -14784,6 +14784,8 @@ intel_prepare_plane_fb(struct drm_plane *plane,
>  						      GFP_KERNEL);
>  		if (ret < 0)
>  			return ret;
> +
> +		i915_gem_object_wait_priority(obj, 0, I915_PRIORITY_DISPLAY);
>  	}
>
>  	if (plane->type == DRM_PLANE_TYPE_CURSOR &&
>

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

Regards,

Tvrtko
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