drm/i915/region: support volatile objects

Volatile objects are marked as DONTNEED while pinned, therefore once
unpinned the backing store can be discarded. This is limited to kernel
internal objects.
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: CQ Tang <cq.tang@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20191008160116.18379-4-matthew.auld@intel.com

drivers/gpu/drm/i915/gem/i915_gem_internal.c

@@ -117,13 +117,6 @@ static int i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj)
 		goto err;
 	}
 
-	/* Mark the pages as dontneed whilst they are still pinned. As soon
-	 * as they are unpinned they are allowed to be reaped by the shrinker,
-	 * and the caller is expected to repopulate - the contents of this
-	 * object are only valid whilst active and pinned.
-	 */
-	obj->mm.madv = I915_MADV_DONTNEED;
-
 	__i915_gem_object_set_pages(obj, st, sg_page_sizes);
 
 	return 0;
@@ -143,7 +136,6 @@ static void i915_gem_object_put_pages_internal(struct drm_i915_gem_object *obj,
 	internal_free_pages(pages);
 
 	obj->mm.dirty = false;
-	obj->mm.madv = I915_MADV_WILLNEED;
 }
 
 static const struct drm_i915_gem_object_ops i915_gem_object_internal_ops = {
@@ -188,6 +180,15 @@ i915_gem_object_create_internal(struct drm_i915_private *i915,
 	drm_gem_private_object_init(&i915->drm, &obj->base, size);
 	i915_gem_object_init(obj, &i915_gem_object_internal_ops);
 
+	/*
+	 * Mark the object as volatile, such that the pages are marked as
+	 * dontneed whilst they are still pinned. As soon as they are unpinned
+	 * they are allowed to be reaped by the shrinker, and the caller is
+	 * expected to repopulate - the contents of this object are only valid
+	 * whilst active and pinned.
+	 */
+	i915_gem_object_set_volatile(obj);
+
 	obj->read_domains = I915_GEM_DOMAIN_CPU;
 	obj->write_domain = I915_GEM_DOMAIN_CPU;
 

drivers/gpu/drm/i915/gem/i915_gem_object.h

@@ -145,6 +145,18 @@ i915_gem_object_is_contiguous(const struct drm_i915_gem_object *obj)
 	return obj->flags & I915_BO_ALLOC_CONTIGUOUS;
 }
 
+static inline bool
+i915_gem_object_is_volatile(const struct drm_i915_gem_object *obj)
+{
+	return obj->flags & I915_BO_ALLOC_VOLATILE;
+}
+
+static inline void
+i915_gem_object_set_volatile(struct drm_i915_gem_object *obj)
+{
+	obj->flags |= I915_BO_ALLOC_VOLATILE;
+}
+
 static inline bool
 i915_gem_object_type_has(const struct drm_i915_gem_object *obj,
 			 unsigned long flags)

drivers/gpu/drm/i915/gem/i915_gem_object_types.h

@@ -121,7 +121,8 @@ struct drm_i915_gem_object {
 
 	unsigned long flags;
 #define I915_BO_ALLOC_CONTIGUOUS BIT(0)
-#define I915_BO_ALLOC_FLAGS (I915_BO_ALLOC_CONTIGUOUS)
+#define I915_BO_ALLOC_VOLATILE   BIT(1)
+#define I915_BO_ALLOC_FLAGS (I915_BO_ALLOC_CONTIGUOUS | I915_BO_ALLOC_VOLATILE)
 
 	/*
 	 * Is the object to be mapped as read-only to the GPU
@@ -172,6 +173,12 @@ struct drm_i915_gem_object {
 		 * List of memory region blocks allocated for this object.
 		 */
 		struct list_head blocks;
+		/**
+		 * Element within memory_region->objects or region->purgeable
+		 * if the object is marked as DONTNEED. Access is protected by
+		 * region->obj_lock.
+		 */
+		struct list_head region_link;
 
 		struct sg_table *pages;
 		void *mapping;

drivers/gpu/drm/i915/gem/i915_gem_pages.c

@@ -18,6 +18,9 @@ void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
 
 	lockdep_assert_held(&obj->mm.lock);
 
+	if (i915_gem_object_is_volatile(obj))
+		obj->mm.madv = I915_MADV_DONTNEED;
+
 	/* Make the pages coherent with the GPU (flushing any swapin). */
 	if (obj->cache_dirty) {
 		obj->write_domain = 0;
@@ -160,6 +163,9 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
 	if (IS_ERR_OR_NULL(pages))
 		return pages;
 
+	if (i915_gem_object_is_volatile(obj))
+		obj->mm.madv = I915_MADV_WILLNEED;
+
 	i915_gem_object_make_unshrinkable(obj);
 
 	if (obj->mm.mapping) {

drivers/gpu/drm/i915/gem/i915_gem_region.c

@@ -107,11 +107,26 @@ void i915_gem_object_init_memory_region(struct drm_i915_gem_object *obj,
 	INIT_LIST_HEAD(&obj->mm.blocks);
 	obj->mm.region = intel_memory_region_get(mem);
 	obj->flags |= flags;
+
+	mutex_lock(&mem->objects.lock);
+
+	if (obj->flags & I915_BO_ALLOC_VOLATILE)
+		list_add(&obj->mm.region_link, &mem->objects.purgeable);
+	else
+		list_add(&obj->mm.region_link, &mem->objects.list);
+
+	mutex_unlock(&mem->objects.lock);
 }
 
 void i915_gem_object_release_memory_region(struct drm_i915_gem_object *obj)
 {
-	intel_memory_region_put(obj->mm.region);
+	struct intel_memory_region *mem = obj->mm.region;
+
+	mutex_lock(&mem->objects.lock);
+	list_del(&obj->mm.region_link);
+	mutex_unlock(&mem->objects.lock);
+
+	intel_memory_region_put(mem);
 }
 
 struct drm_i915_gem_object *

drivers/gpu/drm/i915/gem/selftests/huge_pages.c

@@ -115,8 +115,6 @@ static int get_huge_pages(struct drm_i915_gem_object *obj)
 	if (i915_gem_gtt_prepare_pages(obj, st))
 		goto err;
 
-	obj->mm.madv = I915_MADV_DONTNEED;
-
 	GEM_BUG_ON(sg_page_sizes != obj->mm.page_mask);
 	__i915_gem_object_set_pages(obj, st, sg_page_sizes);
 
@@ -137,7 +135,6 @@ static void put_huge_pages(struct drm_i915_gem_object *obj,
 	huge_pages_free_pages(pages);
 
 	obj->mm.dirty = false;
-	obj->mm.madv = I915_MADV_WILLNEED;
 }
 
 static const struct drm_i915_gem_object_ops huge_page_ops = {
@@ -170,6 +167,8 @@ huge_pages_object(struct drm_i915_private *i915,
 	drm_gem_private_object_init(&i915->drm, &obj->base, size);
 	i915_gem_object_init(obj, &huge_page_ops);
 
+	i915_gem_object_set_volatile(obj);
+
 	obj->write_domain = I915_GEM_DOMAIN_CPU;
 	obj->read_domains = I915_GEM_DOMAIN_CPU;
 	obj->cache_level = I915_CACHE_NONE;
@@ -229,8 +228,6 @@ static int fake_get_huge_pages(struct drm_i915_gem_object *obj)
 
 	i915_sg_trim(st);
 
-	obj->mm.madv = I915_MADV_DONTNEED;
-
 	__i915_gem_object_set_pages(obj, st, sg_page_sizes);
 
 	return 0;
@@ -263,8 +260,6 @@ static int fake_get_huge_pages_single(struct drm_i915_gem_object *obj)
 	sg_dma_len(sg) = obj->base.size;
 	sg_dma_address(sg) = page_size;
 
-	obj->mm.madv = I915_MADV_DONTNEED;
-
 	__i915_gem_object_set_pages(obj, st, sg->length);
 
 	return 0;
@@ -283,7 +278,6 @@ static void fake_put_huge_pages(struct drm_i915_gem_object *obj,
 {
 	fake_free_huge_pages(obj, pages);
 	obj->mm.dirty = false;
-	obj->mm.madv = I915_MADV_WILLNEED;
 }
 
 static const struct drm_i915_gem_object_ops fake_ops = {
@@ -323,6 +317,8 @@ fake_huge_pages_object(struct drm_i915_private *i915, u64 size, bool single)
 	else
 		i915_gem_object_init(obj, &fake_ops);
 
+	i915_gem_object_set_volatile(obj);
+
 	obj->write_domain = I915_GEM_DOMAIN_CPU;
 	obj->read_domains = I915_GEM_DOMAIN_CPU;
 	obj->cache_level = I915_CACHE_NONE;

drivers/gpu/drm/i915/intel_memory_region.c

@@ -152,6 +152,10 @@ intel_memory_region_create(struct drm_i915_private *i915,
 	mem->min_page_size = min_page_size;
 	mem->ops = ops;
 
+	mutex_init(&mem->objects.lock);
+	INIT_LIST_HEAD(&mem->objects.list);
+	INIT_LIST_HEAD(&mem->objects.purgeable);
+
 	mutex_init(&mem->mm_lock);
 
 	if (ops->init) {
@@ -177,6 +181,7 @@ static void __intel_memory_region_destroy(struct kref *kref)
 		mem->ops->release(mem);
 
 	mutex_destroy(&mem->mm_lock);
+	mutex_destroy(&mem->objects.lock);
 	kfree(mem);
 }
 

drivers/gpu/drm/i915/intel_memory_region.h

@@ -52,6 +52,12 @@ struct intel_memory_region {
 	unsigned int type;
 	unsigned int instance;
 	unsigned int id;
+
+	struct {
+		struct mutex lock; /* Protects access to objects */
+		struct list_head list;
+		struct list_head purgeable;
+	} objects;
 };
 
 int intel_memory_region_init_buddy(struct intel_memory_region *mem);

drivers/gpu/drm/i915/selftests/i915_gem_gtt.c

@@ -82,8 +82,6 @@ static int fake_get_pages(struct drm_i915_gem_object *obj)
 	}
 	GEM_BUG_ON(rem);
 
-	obj->mm.madv = I915_MADV_DONTNEED;
-
 	__i915_gem_object_set_pages(obj, pages, sg_page_sizes);
 
 	return 0;
@@ -95,7 +93,6 @@ static void fake_put_pages(struct drm_i915_gem_object *obj,
 {
 	fake_free_pages(obj, pages);
 	obj->mm.dirty = false;
-	obj->mm.madv = I915_MADV_WILLNEED;
 }
 
 static const struct drm_i915_gem_object_ops fake_ops = {
@@ -122,6 +119,8 @@ fake_dma_object(struct drm_i915_private *i915, u64 size)
 	drm_gem_private_object_init(&i915->drm, &obj->base, size);
 	i915_gem_object_init(obj, &fake_ops);
 
+	i915_gem_object_set_volatile(obj);
+
 	obj->write_domain = I915_GEM_DOMAIN_CPU;
 	obj->read_domains = I915_GEM_DOMAIN_CPU;
 	obj->cache_level = I915_CACHE_NONE;