drm/i915: Add ioctl to set 'purgeability' of objects

Similar to the madvise() concept, the application may wish to mark some
data as volatile. That is in the event of memory pressure the kernel is
free to discard such buffers safe in the knowledge that the application
can recreate them on demand, and is simply using these as a cache.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

3 files changed, 81 insertions, 8 deletions

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index f47adb4aa59a..250999cdf814 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1616,6 +1616,7 @@ struct drm_ioctl_desc i915_ioctls[] = {
 	DRM_IOCTL_DEF(DRM_I915_GEM_GET_TILING, i915_gem_get_tiling, 0),
 	DRM_IOCTL_DEF(DRM_I915_GEM_GET_APERTURE, i915_gem_get_aperture_ioctl, 0),
 	DRM_IOCTL_DEF(DRM_I915_GET_PIPE_FROM_CRTC_ID, intel_get_pipe_from_crtc_id, 0),
+	DRM_IOCTL_DEF(DRM_I915_GEM_MADVISE, i915_gem_madvise_ioctl, 0),
 };
 
 int i915_max_ioctl = DRM_ARRAY_SIZE(i915_ioctls);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index bbcf5fc72666..2f89c2136be9 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -566,6 +566,11 @@ struct drm_i915_gem_object {
 	 * in an execbuffer object list.
 	 */
 	int in_execbuffer;
+
+	/**
+	 * Advice: are the backing pages purgeable?
+	 */
+	int madv;
 };
 
 /**
@@ -705,6 +710,8 @@ int i915_gem_busy_ioctl(struct drm_device *dev, void *data,
 			struct drm_file *file_priv);
 int i915_gem_throttle_ioctl(struct drm_device *dev, void *data,
 			    struct drm_file *file_priv);
+int i915_gem_madvise_ioctl(struct drm_device *dev, void *data,
+			   struct drm_file *file_priv);
 int i915_gem_entervt_ioctl(struct drm_device *dev, void *data,
 			   struct drm_file *file_priv);
 int i915_gem_leavevt_ioctl(struct drm_device *dev, void *data,
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 2fff2e0a976e..2ab30f251943 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1436,13 +1436,21 @@ i915_gem_object_put_pages(struct drm_gem_object *obj)
 	if (obj_priv->tiling_mode != I915_TILING_NONE)
 		i915_gem_object_save_bit_17_swizzle(obj);
 
-	for (i = 0; i < page_count; i++)
-		if (obj_priv->pages[i] != NULL) {
-			if (obj_priv->dirty)
-				set_page_dirty(obj_priv->pages[i]);
-			mark_page_accessed(obj_priv->pages[i]);
-			page_cache_release(obj_priv->pages[i]);
-		}
+	if (obj_priv->madv == I915_MADV_DONTNEED)
+	    obj_priv->dirty = 0;
+
+	for (i = 0; i < page_count; i++) {
+		if (obj_priv->pages[i] == NULL)
+			break;
+
+		if (obj_priv->dirty)
+			set_page_dirty(obj_priv->pages[i]);
+
+		if (obj_priv->madv == I915_MADV_WILLNEED)
+		    mark_page_accessed(obj_priv->pages[i]);
+
+		page_cache_release(obj_priv->pages[i]);
+	}
 	obj_priv->dirty = 0;
 
 	drm_free_large(obj_priv->pages);
@@ -2412,6 +2420,12 @@ i915_gem_object_bind_to_gtt(struct drm_gem_object *obj, unsigned alignment)
 
 	if (dev_priv->mm.suspended)
 		return -EBUSY;
+
+	if (obj_priv->madv == I915_MADV_DONTNEED) {
+		DRM_ERROR("Attempting to bind a purgeable object\n");
+		return -EINVAL;
+	}
+
 	if (alignment == 0)
 		alignment = i915_gem_get_gtt_alignment(obj);
 	if (alignment & (i915_gem_get_gtt_alignment(obj) - 1)) {
@@ -3679,6 +3693,13 @@ i915_gem_pin_ioctl(struct drm_device *dev, void *data,
 	}
 	obj_priv = obj->driver_private;
 
+	if (obj_priv->madv == I915_MADV_DONTNEED) {
+		DRM_ERROR("Attempting to pin a I915_MADV_DONTNEED buffer\n");
+		drm_gem_object_unreference(obj);
+		mutex_unlock(&dev->struct_mutex);
+		return -EINVAL;
+	}
+
 	if (obj_priv->pin_filp != NULL && obj_priv->pin_filp != file_priv) {
 		DRM_ERROR("Already pinned in i915_gem_pin_ioctl(): %d\n",
 			  args->handle);
@@ -3791,6 +3812,49 @@ i915_gem_throttle_ioctl(struct drm_device *dev, void *data,
     return i915_gem_ring_throttle(dev, file_priv);
 }
 
+int
+i915_gem_madvise_ioctl(struct drm_device *dev, void *data,
+		       struct drm_file *file_priv)
+{
+	struct drm_i915_gem_madvise *args = data;
+	struct drm_gem_object *obj;
+	struct drm_i915_gem_object *obj_priv;
+
+	switch (args->madv) {
+	case I915_MADV_DONTNEED:
+	case I915_MADV_WILLNEED:
+	    break;
+	default:
+	    return -EINVAL;
+	}
+
+	obj = drm_gem_object_lookup(dev, file_priv, args->handle);
+	if (obj == NULL) {
+		DRM_ERROR("Bad handle in i915_gem_madvise_ioctl(): %d\n",
+			  args->handle);
+		return -EBADF;
+	}
+
+	mutex_lock(&dev->struct_mutex);
+	obj_priv = obj->driver_private;
+
+	if (obj_priv->pin_count) {
+		drm_gem_object_unreference(obj);
+		mutex_unlock(&dev->struct_mutex);
+
+		DRM_ERROR("Attempted i915_gem_madvise_ioctl() on a pinned object\n");
+		return -EINVAL;
+	}
+
+	obj_priv->madv = args->madv;
+	args->retained = obj_priv->gtt_space != NULL;
+
+	drm_gem_object_unreference(obj);
+	mutex_unlock(&dev->struct_mutex);
+
+	return 0;
+}
+
 int i915_gem_init_object(struct drm_gem_object *obj)
 {
 	struct drm_i915_gem_object *obj_priv;
@@ -3815,6 +3879,7 @@ int i915_gem_init_object(struct drm_gem_object *obj)
 	obj_priv->fence_reg = I915_FENCE_REG_NONE;
 	INIT_LIST_HEAD(&obj_priv->list);
 	INIT_LIST_HEAD(&obj_priv->fence_list);
+	obj_priv->madv = I915_MADV_WILLNEED;
 
 	return 0;
 }
@@ -4506,7 +4571,7 @@ i915_gem_object_truncate(struct drm_gem_object *obj)
 static inline int
 i915_gem_object_is_purgeable(struct drm_i915_gem_object *obj_priv)
 {
-	return !obj_priv->dirty;
+	return !obj_priv->dirty || obj_priv->madv == I915_MADV_DONTNEED;
 }
 
 static int