[Intel-gfx] [PATCH 3/4] drm/i915: Add support for stealing purgable stolen pages

[Tvrtko Ursulin]

On 07/01/2015 10:25 AM, ankitprasad.r.sharma at intel.com wrote:
> From: Chris Wilson <chris at chris-wilson.co.uk>
>
> If we run out of stolen memory when trying to allocate an object, see if
> we can reap enough purgeable objects to free up enough contiguous free
> space for the allocation. This is in principle very much like evicting
> objects to free up enough contiguous space in the vma when binding
> a new object - and you will be forgiven for thinking that the code looks
> very similar.
>
> At the moment, we do not allow userspace to allocate objects in stolen,
> so there is neither the memory pressure to trigger stolen eviction nor
> any purgeable objects inside the stolen arena. However, this will change
> in the near future, and so better management and defragmentation of
> stolen memory will become a real issue.
>
> v2: Remember to remove the drm_mm_node.
>
> v3: Rebased to the latest drm-intel-nightly (Ankit)
>
> testcase: igt/gem_stolen
>

Tidy "Testcase:" tag again.

> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/i915/i915_gem_stolen.c | 121 ++++++++++++++++++++++++++++++---
>   1 file changed, 110 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
> index 348ed5a..7e216be 100644
> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> @@ -430,18 +430,29 @@ cleanup:
>   	return NULL;
>   }
>
> -struct drm_i915_gem_object *
> -i915_gem_object_create_stolen(struct drm_device *dev, u32 size)
> +static bool mark_free(struct drm_i915_gem_object *obj, struct list_head *unwind)
> +{
> +	if (obj->stolen == NULL)
> +		return false;
> +
> +	if (obj->madv != I915_MADV_DONTNEED)
> +		return false;
> +
> +	if (i915_gem_obj_is_pinned(obj))
> +		return false;
> +
> +	list_add(&obj->obj_exec_link, unwind);
> +	return drm_mm_scan_add_block(obj->stolen);
> +}
> +
> +static struct drm_mm_node *
> +stolen_alloc(struct drm_i915_private *dev_priv, u32 size)
>   {
> -	struct drm_i915_private *dev_priv = dev->dev_private;
> -	struct drm_i915_gem_object *obj;
>   	struct drm_mm_node *stolen;
> +	struct drm_i915_gem_object *obj;
> +	struct list_head unwind, evict;
>   	int ret;
>
> -	if (!drm_mm_initialized(&dev_priv->mm.stolen))
> -		return NULL;
> -
> -	DRM_DEBUG_KMS("creating stolen object: size=%x\n", size);
>   	if (size == 0)
>   		return NULL;
>
> @@ -451,11 +462,99 @@ i915_gem_object_create_stolen(struct drm_device *dev, u32 size)
>
>   	ret = drm_mm_insert_node(&dev_priv->mm.stolen, stolen, size,
>   				 4096, DRM_MM_SEARCH_DEFAULT);
> -	if (ret) {
> -		kfree(stolen);
> -		return NULL;
> +	if (ret == 0)
> +		return stolen;
> +
> +	/* No more stolen memory available, or too fragmented.
> +	 * Try evicting purgeable objects and search again.
> +	 */
> +
> +	drm_mm_init_scan(&dev_priv->mm.stolen, size, 4096, 0);
> +	INIT_LIST_HEAD(&unwind);
> +
> +	list_for_each_entry(obj, &dev_priv->mm.unbound_list, global_list)
> +		if (mark_free(obj, &unwind))
> +			goto found;
> +
> +	list_for_each_entry(obj, &dev_priv->mm.bound_list, global_list)
> +		if (mark_free(obj, &unwind))
> +			goto found;
> +
> +found:
> +	INIT_LIST_HEAD(&evict);
> +	while (!list_empty(&unwind)) {
> +		obj = list_first_entry(&unwind,
> +				       struct drm_i915_gem_object,
> +				       obj_exec_link);
> +		list_del_init(&obj->obj_exec_link);
> +
> +		if (drm_mm_scan_remove_block(obj->stolen)) {
> +			list_add(&obj->obj_exec_link, &evict);
> +			drm_gem_object_reference(&obj->base);
> +		}
>   	}
>
> +	ret = 0;
> +	while (!list_empty(&evict)) {
> +		obj = list_first_entry(&evict,
> +				       struct drm_i915_gem_object,
> +				       obj_exec_link);
> +		list_del_init(&obj->obj_exec_link);
> +
> +		if (ret == 0) {
> +			struct i915_vma *vma, *vma_next;
> +
> +			list_for_each_entry_safe(vma, vma_next,
> +						 &obj->vma_list,
> +						 vma_link)
> +				if (i915_vma_unbind(vma))
> +					break;
> +
> +			/* Stolen pins its pages to prevent the
> +			 * normal shrinker from processing stolen
> +			 * objects.
> +			 */
> +			i915_gem_object_unpin_pages(obj);
> +
> +			ret = i915_gem_object_put_pages(obj);
> +			if (ret == 0) {
> +				i915_gem_object_release_stolen(obj);
> +				obj->madv = __I915_MADV_PURGED;
> +			} else
> +				i915_gem_object_pin_pages(obj);

Both blocks need curly braces if one has them.

With these two tiny details fixed,

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

Regards,

Tvrtko