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Commit 8bd81815 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Skip waking the device to service pwrite 



If the device is in runtime suspend, resuming takes time and reduces our
powersaving. If this was for a small write into an object, that resume
will take longer than any savings in using the indirect GGTT access to
avoid the cpu cache.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20171019063733.31620-1-chris@chris-wilson.co.uk
parent 2f26cdc0

drivers/gpu/drm/i915/i915_gem.c

+20 −3
Original line number Diff line number Diff line
@@ -1240,7 +1240,23 @@ i915_gem_gtt_pwrite_fast(struct drm_i915_gem_object *obj, 
	if (ret)

		return ret;



	if (i915_gem_object_has_struct_page(obj)) {

		/*

		 * Avoid waking the device up if we can fallback, as

		 * waking/resuming is very slow (worst-case 10-100 ms

		 * depending on PCI sleeps and our own resume time).

		 * This easily dwarfs any performance advantage from

		 * using the cache bypass of indirect GGTT access.

		 */

		if (!intel_runtime_pm_get_if_in_use(i915)) {

			ret = -EFAULT;

			goto out_unlock;

		}

	} else {

		/* No backing pages, no fallback, we must force GGTT access */

		intel_runtime_pm_get(i915);

	}



	vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0,

				       PIN_MAPPABLE |

				       PIN_NONFAULT |
@@ -1257,7 +1273,7 @@ i915_gem_gtt_pwrite_fast(struct drm_i915_gem_object *obj, 
	if (IS_ERR(vma)) {

		ret = insert_mappable_node(ggtt, &node, PAGE_SIZE);

		if (ret)

			goto out_unlock;

			goto out_rpm;

		GEM_BUG_ON(!node.allocated);

	}
@@ -1320,8 +1336,9 @@ i915_gem_gtt_pwrite_fast(struct drm_i915_gem_object *obj, 
	} else {

		i915_vma_unpin(vma);

	}

out_unlock:

out_rpm:

	intel_runtime_pm_put(i915);

out_unlock:

	mutex_unlock(&i915->drm.struct_mutex);

	return ret;

}