From ad16d2ed8fa80e7f4f0d0da32129ed2c9caca3b4 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 13 Oct 2016 09:55:04 +0100 Subject: [PATCH] drm/i915: Skip unbinding large unmappable global buffers If the user requests a mappable binding to the global GTT, we will first unbind an existing mapping if it doesn't match. We will unbind even if there is no possibility that the object can fit in the mappable aperture. This may lead to a ping-pong migration of the object, for example igt/gem_exec_big. v2: Comment upon the reasoning, or lack thereof!, behind the choice of magic numbers. Testcase: igt/gem_exec_big Signed-off-by: Chris Wilson Link: http://patchwork.freedesktop.org/patch/msgid/20161013085504.30705-1-chris@chris-wilson.co.uk Reviewed-by: Tvrtko Ursulin node.start < start); + GEM_BUG_ON(vma->node.start + vma->node.size > end); } GEM_BUG_ON(!i915_gem_valid_gtt_space(vma, obj->cache_level)); @@ -3798,7 +3801,8 @@ i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj, u64 alignment, u64 flags) { - struct i915_address_space *vm = &to_i915(obj->base.dev)->ggtt.base; + struct drm_i915_private *dev_priv = to_i915(obj->base.dev); + struct i915_address_space *vm = &dev_priv->ggtt.base; struct i915_vma *vma; int ret; @@ -3811,6 +3815,41 @@ i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj, (i915_vma_is_pinned(vma) || i915_vma_is_active(vma))) return ERR_PTR(-ENOSPC); + if (flags & PIN_MAPPABLE) { + u32 fence_size; + + fence_size = i915_gem_get_ggtt_size(dev_priv, vma->size, + i915_gem_object_get_tiling(obj)); + /* If the required space is larger than the available + * aperture, we will not able to find a slot for the + * object and unbinding the object now will be in + * vain. Worse, doing so may cause us to ping-pong + * the object in and out of the Global GTT and + * waste a lot of cycles under the mutex. + */ + if (fence_size > dev_priv->ggtt.mappable_end) + return ERR_PTR(-E2BIG); + + /* If NONBLOCK is set the caller is optimistically + * trying to cache the full object within the mappable + * aperture, and *must* have a fallback in place for + * situations where we cannot bind the object. We + * can be a little more lax here and use the fallback + * more often to avoid costly migrations of ourselves + * and other objects within the aperture. + * + * Half-the-aperture is used as a simple heuristic. + * More interesting would to do search for a free + * block prior to making the commitment to unbind. + * That caters for the self-harm case, and with a + * little more heuristics (e.g. NOFAULT, NOEVICT) + * we could try to minimise harm to others. + */ + if (flags & PIN_NONBLOCK && + fence_size > dev_priv->ggtt.mappable_end / 2) + return ERR_PTR(-ENOSPC); + } + WARN(i915_vma_is_pinned(vma), "bo is already pinned in ggtt with incorrect alignment:" " offset=%08x, req.alignment=%llx," -- 2.20.1