drm/i915: Register a shrinker to free inactive lists under memory pressure

This should help GEM handle memory pressure sitatuions more gracefully.

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

3 files changed, 159 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 1f9e4503b072..c57c1744cecf 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -362,6 +362,8 @@ static int __init i915_init(void)
 {
         driver.num_ioctls = i915_max_ioctl;
 
+        i915_gem_shrinker_init();
+
         /*
          * If CONFIG_DRM_I915_KMS is set, default to KMS unless
          * explicitly disabled with the module pararmeter.
@@ -388,6 +390,7 @@ static int __init i915_init(void)
 
 static void __exit i915_exit(void)
 {
+        i915_gem_shrinker_exit();
         drm_exit(&driver);
 }
 
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 07214694b14f..bbcf5fc72666 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -369,6 +369,15 @@ typedef struct drm_i915_private {
                 int gtt_mtrr;
 
                 /**
+                 * Membership on list of all loaded devices, used to evict
+                 * inactive buffers under memory pressure.
+                 *
+                 * Modifications should only be done whilst holding the
+                 * shrink_list_lock spinlock.
+                 */
+                struct list_head shrink_list;
+
+                /**
                  * List of objects currently involved in rendering from the
                  * ringbuffer.
                  *
@@ -741,6 +750,9 @@ int i915_gem_object_get_pages(struct drm_gem_object *obj);
 void i915_gem_object_put_pages(struct drm_gem_object *obj);
 void i915_gem_release(struct drm_device * dev, struct drm_file *file_priv);
 
+void i915_gem_shrinker_init(void);
+void i915_gem_shrinker_exit(void);
+
 /* i915_gem_tiling.c */
 void i915_gem_detect_bit_6_swizzle(struct drm_device *dev);
 void i915_gem_object_do_bit_17_swizzle(struct drm_gem_object *obj);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 77cc6f57166c..2fff2e0a976e 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -53,6 +53,9 @@ static int i915_gem_phys_pwrite(struct drm_device *dev, struct drm_gem_object *o
                                 struct drm_i915_gem_pwrite *args,
                                 struct drm_file *file_priv);
 
+static LIST_HEAD(shrink_list);
+static DEFINE_SPINLOCK(shrink_list_lock);
+
 int i915_gem_do_init(struct drm_device *dev, unsigned long start,
                      unsigned long end)
 {
@@ -4265,6 +4268,10 @@ i915_gem_load(struct drm_device *dev)
                           i915_gem_retire_work_handler);
         dev_priv->mm.next_gem_seqno = 1;
 
+        spin_lock(&shrink_list_lock);
+        list_add(&dev_priv->mm.shrink_list, &shrink_list);
+        spin_unlock(&shrink_list_lock);
+
         /* Old X drivers will take 0-2 for front, back, depth buffers */
         dev_priv->fence_reg_start = 3;
 
@@ -4482,3 +4489,140 @@ void i915_gem_release(struct drm_device * dev, struct drm_file *file_priv)
                 list_del_init(i915_file_priv->mm.request_list.next);
         mutex_unlock(&dev->struct_mutex);
 }
+
+/* Immediately discard the backing storage */
+static void
+i915_gem_object_truncate(struct drm_gem_object *obj)
+{
+    struct inode *inode;
+
+    inode = obj->filp->f_path.dentry->d_inode;
+
+    mutex_lock(&inode->i_mutex);
+    truncate_inode_pages(inode->i_mapping, 0);
+    mutex_unlock(&inode->i_mutex);
+}
+
+static inline int
+i915_gem_object_is_purgeable(struct drm_i915_gem_object *obj_priv)
+{
+        return !obj_priv->dirty;
+}
+
+static int
+i915_gem_shrink(int nr_to_scan, gfp_t gfp_mask)
+{
+        drm_i915_private_t *dev_priv, *next_dev;
+        struct drm_i915_gem_object *obj_priv, *next_obj;
+        int cnt = 0;
+        int would_deadlock = 1;
+
+        /* "fast-path" to count number of available objects */
+        if (nr_to_scan == 0) {
+                spin_lock(&shrink_list_lock);
+                list_for_each_entry(dev_priv, &shrink_list, mm.shrink_list) {
+                        struct drm_device *dev = dev_priv->dev;
+
+                        if (mutex_trylock(&dev->struct_mutex)) {
+                                list_for_each_entry(obj_priv,
+                                                    &dev_priv->mm.inactive_list,
+                                                    list)
+                                        cnt++;
+                                mutex_unlock(&dev->struct_mutex);
+                        }
+                }
+                spin_unlock(&shrink_list_lock);
+
+                return (cnt / 100) * sysctl_vfs_cache_pressure;
+        }
+
+        spin_lock(&shrink_list_lock);
+
+        /* first scan for clean buffers */
+        list_for_each_entry_safe(dev_priv, next_dev,
+                                 &shrink_list, mm.shrink_list) {
+                struct drm_device *dev = dev_priv->dev;
+
+                if (! mutex_trylock(&dev->struct_mutex))
+                        continue;
+
+                spin_unlock(&shrink_list_lock);
+
+                i915_gem_retire_requests(dev);
+
+                list_for_each_entry_safe(obj_priv, next_obj,
+                                         &dev_priv->mm.inactive_list,
+                                         list) {
+                        if (i915_gem_object_is_purgeable(obj_priv)) {
+                                struct drm_gem_object *obj = obj_priv->obj;
+                                i915_gem_object_unbind(obj);
+                                i915_gem_object_truncate(obj);
+
+                                if (--nr_to_scan <= 0)
+                                        break;
+                        }
+                }
+
+                spin_lock(&shrink_list_lock);
+                mutex_unlock(&dev->struct_mutex);
+
+                if (nr_to_scan <= 0)
+                        break;
+        }
+
+        /* second pass, evict/count anything still on the inactive list */
+        list_for_each_entry_safe(dev_priv, next_dev,
+                                 &shrink_list, mm.shrink_list) {
+                struct drm_device *dev = dev_priv->dev;
+
+                if (! mutex_trylock(&dev->struct_mutex))
+                        continue;
+
+                spin_unlock(&shrink_list_lock);
+
+                list_for_each_entry_safe(obj_priv, next_obj,
+                                         &dev_priv->mm.inactive_list,
+                                         list) {
+                        if (nr_to_scan > 0) {
+                                struct drm_gem_object *obj = obj_priv->obj;
+                                i915_gem_object_unbind(obj);
+                                if (i915_gem_object_is_purgeable(obj_priv))
+                                        i915_gem_object_truncate(obj);
+
+                                nr_to_scan--;
+                        } else
+                                cnt++;
+                }
+
+                spin_lock(&shrink_list_lock);
+                mutex_unlock(&dev->struct_mutex);
+
+                would_deadlock = 0;
+        }
+
+        spin_unlock(&shrink_list_lock);
+
+        if (would_deadlock)
+                return -1;
+        else if (cnt > 0)
+                return (cnt / 100) * sysctl_vfs_cache_pressure;
+        else
+                return 0;
+}
+
+static struct shrinker shrinker = {
+        .shrink = i915_gem_shrink,
+        .seeks = DEFAULT_SEEKS,
+};
+
+__init void
+i915_gem_shrinker_init(void)
+{
+    register_shrinker(&shrinker);
+}
+
+__exit void
+i915_gem_shrinker_exit(void)
+{
+    unregister_shrinker(&shrinker);
+}