[Intel-gfx] [PATCH v4 1/7] drm/i915: Implement a framework for batch buffer pools

[Chris Wilson]

On Fri, Nov 07, 2014 at 02:22:01PM -0800, bradley.d.volkin at intel.com wrote:
> +struct drm_i915_gem_object *
> +i915_gem_batch_pool_get(struct i915_gem_batch_pool *pool,
> +			size_t size)
> +{
> +	struct drm_i915_gem_object *obj = NULL;
> +	struct drm_i915_gem_object *tmp, *next;
> +	bool was_purged;
> +
> +	WARN_ON(!mutex_is_locked(&pool->dev->struct_mutex));
> +
> +	list_for_each_entry_safe(tmp, next,
> +				 &pool->active_list, batch_pool_list) {
> +		if (!tmp->active)
> +			list_move_tail(&tmp->batch_pool_list,
> +				       &pool->inactive_list);
> +	}

So we don't need two lists then?

> +	do {
> +		was_purged = false;
> +
> +		list_for_each_entry(tmp, &pool->inactive_list, batch_pool_list) {
> +			/*
> +			 * Select a buffer that is at least as big as needed
> +			 * but not 'too much' bigger. A better way to do this
> +			 * might be to bucket the pool objects based on size.
> +			 */
> +			if (tmp->base.size >= size &&
> +			    tmp->base.size <= (2 * size)) {
> +				obj = tmp;
> +				break;
> +			}
> +		}
> +
> +		if (obj && obj->madv == __I915_MADV_PURGED) {
> +			was_purged = true;
> +			list_del(&obj->batch_pool_list);
> +			drm_gem_object_unreference(&obj->base);
> +			obj = NULL;
> +		}
> +	} while (was_purged);

You stop searching if you find an inactive buffer too big or too small?

> +
> +	if (!obj) {
> +		obj = i915_gem_alloc_object(pool->dev, size);
> +		if (!obj)
> +			return ERR_PTR(-ENOMEM);

Grag pages and set the madv here, don't ever worry about it again later.

> +		list_add_tail(&obj->batch_pool_list, &pool->inactive_list);

Redundant.

> +	}
> +
> +	list_move_tail(&obj->batch_pool_list, &pool->active_list);
> +
> +	return obj;
> +}

-- 
Chris Wilson, Intel Open Source Technology Centre