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Commit 3d574a6b authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Remove walk over obj->vma_list for the shrinker 



In the next patch, we want to reduce the lock coverage within the
shrinker, and one of the dangerous walks we have is over obj->vma_list.
We are only walking the obj->vma_list in order to check whether it has
been permanently pinned by HW access, typically via use on the scanout.
But we have a couple of other long term pins, the context objects for
which we currently have to check the individual vma pin_count. If we
instead mark these using obj->pin_display, we can forgo the dangerous
and sometimes slow list iteration.

v2: Rearrange code to try and avoid confusion from false associations
due to arrangement of whitespace along with rebasing on obj->pin_global.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171013202621.7276-4-chris@chris-wilson.co.uk
parent f46250e4

drivers/gpu/drm/i915/i915_gem_shrinker.c

+7 −20
Original line number Diff line number Diff line
@@ -71,25 +71,6 @@ static void shrinker_unlock(struct drm_i915_private *dev_priv, bool unlock) 
	mutex_unlock(&dev_priv->drm.struct_mutex);

}



static bool any_vma_pinned(struct drm_i915_gem_object *obj)

{

	struct i915_vma *vma;



	list_for_each_entry(vma, &obj->vma_list, obj_link) {

		/* Only GGTT vma may be permanently pinned, and are always

		 * at the start of the list. We can stop hunting as soon

		 * as we see a ppGTT vma.

		 */

		if (!i915_vma_is_ggtt(vma))

			break;



		if (i915_vma_is_pinned(vma))

			return true;

	}



	return false;

}



static bool swap_available(void)

{

	return get_nr_swap_pages() > 0;
@@ -115,7 +96,13 @@ static bool can_release_pages(struct drm_i915_gem_object *obj) 
	if (atomic_read(&obj->mm.pages_pin_count) > obj->bind_count)

		return false;



	if (any_vma_pinned(obj))

	/* If any vma are "permanently" pinned, it will prevent us from

	 * reclaiming the obj->mm.pages. We only allow scanout objects to claim

	 * a permanent pin, along with a few others like the context objects.

	 * To simplify the scan, and to avoid walking the list of vma under the

	 * object, we just check the count of its permanently pinned.

	 */

	if (obj->pin_global)

		return false;



	/* We can only return physical pages to the system if we can either

drivers/gpu/drm/i915/intel_lrc.c

+2 −0
Original line number Diff line number Diff line
@@ -1093,6 +1093,7 @@ execlists_context_pin(struct intel_engine_cs *engine, 
		i915_ggtt_offset(ce->ring->vma);



	ce->state->obj->mm.dirty = true;

	ce->state->obj->pin_global++;



	i915_gem_context_get(ctx);

out:
@@ -1120,6 +1121,7 @@ static void execlists_context_unpin(struct intel_engine_cs *engine, 


	intel_ring_unpin(ce->ring);



	ce->state->obj->pin_global--;

	i915_gem_object_unpin_map(ce->state->obj);

	i915_vma_unpin(ce->state);

drivers/gpu/drm/i915/intel_ringbuffer.c

+7 −1
Original line number Diff line number Diff line
@@ -1244,6 +1244,8 @@ int intel_ring_pin(struct intel_ring *ring, 
	if (IS_ERR(addr))

		goto err;



	vma->obj->pin_global++;



	ring->vaddr = addr;

	return 0;
@@ -1275,6 +1277,7 @@ void intel_ring_unpin(struct intel_ring *ring) 
		i915_gem_object_unpin_map(ring->vma->obj);

	ring->vaddr = NULL;



	ring->vma->obj->pin_global--;

	i915_vma_unpin(ring->vma);

}
@@ -1439,6 +1442,7 @@ intel_ring_context_pin(struct intel_engine_cs *engine, 
			goto err;



		ce->state->obj->mm.dirty = true;

		ce->state->obj->pin_global++;

	}



	/* The kernel context is only used as a placeholder for flushing the
@@ -1473,8 +1477,10 @@ static void intel_ring_context_unpin(struct intel_engine_cs *engine, 
	if (--ce->pin_count)

		return;



	if (ce->state)

	if (ce->state) {

		ce->state->obj->pin_global--;

		i915_vma_unpin(ce->state);

	}



	i915_gem_context_put(ctx);

}