drm/msm: Avoid mutex in shrinker_count()

When the system is under heavy memory pressure, we can end up with lots
of concurrent calls into the shrinker.  Keeping a running tab on what we
can shrink avoids grabbing a lock in shrinker->count(), and avoids
shrinker->scan() getting called when not profitable.

Also, we can keep purged objects in their own list to avoid re-traversing
them to help cut down time in the critical section further.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20210401012722.527712-3-robdclark@gmail.com
Signed-off-by: Rob Clark <robdclark@chromium.org>

1 files changed, 49 insertions, 4 deletions

diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
index 7a9107cf1818..13aabfe92dac 100644
--- a/drivers/gpu/drm/msm/msm_gem.h
+++ b/drivers/gpu/drm/msm/msm_gem.h
@@ -51,17 +51,23 @@ struct msm_gem_object {
 	uint8_t madv;
 
 	/**
+	 * Is object on inactive_dontneed list (ie. counted in priv->shrinkable_count)?
+	 */
+	bool dontneed : 1;
+
+	/**
 	 * count of active vmap'ing
 	 */
 	uint8_t vmap_count;
 
-	/* And object is either:
-	 *  inactive - on priv->inactive_list
+	/**
+	 * An object is either:
+	 *  inactive - on priv->inactive_dontneed/willneed/purged depending
+	 *     on status
 	 *  active   - on one one of the gpu's active_list..  well, at
 	 *     least for now we don't have (I don't think) hw sync between
 	 *     2d and 3d one devices which have both, meaning we need to
 	 *     block on submit if a bo is already on other ring
-	 *
 	 */
 	struct list_head mm_list;
 
@@ -186,10 +192,16 @@ static inline bool is_active(struct msm_gem_object *msm_obj)
 	return msm_obj->active_count;
 }
 
+/* imported/exported objects are not purgable: */
+static inline bool is_unpurgable(struct msm_gem_object *msm_obj)
+{
+	return msm_obj->base.dma_buf && msm_obj->base.import_attach;
+}
+
 static inline bool is_purgeable(struct msm_gem_object *msm_obj)
 {
 	return (msm_obj->madv == MSM_MADV_DONTNEED) && msm_obj->sgt &&
-			!msm_obj->base.dma_buf && !msm_obj->base.import_attach;
+			!is_unpurgable(msm_obj);
 }
 
 static inline bool is_vunmapable(struct msm_gem_object *msm_obj)
@@ -198,6 +210,39 @@ static inline bool is_vunmapable(struct msm_gem_object *msm_obj)
 	return (msm_obj->vmap_count == 0) && msm_obj->vaddr;
 }
 
+static inline void mark_purgable(struct msm_gem_object *msm_obj)
+{
+	struct msm_drm_private *priv = msm_obj->base.dev->dev_private;
+
+	WARN_ON(!mutex_is_locked(&priv->mm_lock));
+
+	if (is_unpurgable(msm_obj))
+		return;
+
+	if (WARN_ON(msm_obj->dontneed))
+		return;
+
+	priv->shrinkable_count += msm_obj->base.size >> PAGE_SHIFT;
+	msm_obj->dontneed = true;
+}
+
+static inline void mark_unpurgable(struct msm_gem_object *msm_obj)
+{
+	struct msm_drm_private *priv = msm_obj->base.dev->dev_private;
+
+	WARN_ON(!mutex_is_locked(&priv->mm_lock));
+
+	if (is_unpurgable(msm_obj))
+		return;
+
+	if (WARN_ON(!msm_obj->dontneed))
+		return;
+
+	priv->shrinkable_count -= msm_obj->base.size >> PAGE_SHIFT;
+	WARN_ON(priv->shrinkable_count < 0);
+	msm_obj->dontneed = false;
+}
+
 void msm_gem_purge(struct drm_gem_object *obj);
 void msm_gem_vunmap(struct drm_gem_object *obj);