[gem] Replace ring throttling hack with actual time measurement.

diff --git a/linux-core/i915_gem.c b/linux-core/i915_gem.c
index 94e2e47..641ca8a 100644 (file)
--- a/linux-core/i915_gem.c
+++ b/linux-core/i915_gem.c
@@ -154,6 +154,7 @@ i915_add_request(struct drm_device *dev)
        DRM_DEBUG("%d\n", seqno);
 
        request->seqno = seqno;
+       request->emitted_jiffies = jiffies;
        list_add_tail(&request->list, &dev_priv->mm.request_list);
 
        return seqno;
@@ -966,34 +967,38 @@ i915_dispatch_gem_execbuffer(struct drm_device *dev,
        return 0;
 }
 
-/*
- * Kludge -- wait for almost all rendering to complete
- * before queuing more. This uses interrupts, so the wakeup
- * occurs without any delay.
+/* Throttle our rendering by waiting until the ring has completed our requests
+ * emitted over 20 msec ago.
+ *
+ * This should get us reasonable parallelism between CPU and GPU but also
+ * relatively low latency when blocking on a particular request to finish.
  */
 static int
-i915_gem_wait_space(struct drm_device *dev)
+i915_gem_ring_throttle(struct drm_device *dev)
 {
        drm_i915_private_t *dev_priv = dev->dev_private;
-       drm_i915_ring_buffer_t *ring = &(dev_priv->ring);
-       struct drm_i915_gem_object *obj_priv, *last_priv = NULL;
        int ret = 0;
 
        mutex_lock(&dev->struct_mutex);
-       while (ring->space + 1024 < dev_priv->ring.Size &&
-              !list_empty(&dev_priv->mm.active_list)) {
-               obj_priv = list_first_entry(&dev_priv->mm.active_list,
-                                           struct drm_i915_gem_object,
-                                           list);
-               if (obj_priv == last_priv)
-                       break;
-               drm_gem_object_reference(obj_priv->obj);
-               ret = i915_gem_object_wait_rendering(obj_priv->obj);
-               drm_gem_object_unreference(obj_priv->obj);
-               if (ret)
-                       break;
-               last_priv = obj_priv;
-               i915_kernel_lost_context(dev);
+       while (!list_empty(&dev_priv->mm.request_list)) {
+               struct drm_i915_gem_request *request;
+
+               request = list_first_entry(&dev_priv->mm.request_list,
+                                          struct drm_i915_gem_request,
+                                          list);
+
+               /* Break out if we're close enough. */
+               if (jiffies_to_msecs(jiffies - request->emitted_jiffies) < 20) {
+                       mutex_unlock(&dev->struct_mutex);
+                       return 0;
+               }
+
+               /* Wait on the last request if not. */
+               ret = i915_wait_request(dev, request->seqno);
+               if (ret != 0) {
+                       mutex_unlock(&dev->struct_mutex);
+                       return ret;
+               }
        }
        mutex_unlock(&dev->struct_mutex);
        return ret;
@@ -1019,7 +1024,7 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
 #endif
        i915_kernel_lost_context(dev);
 
-       ret = i915_gem_wait_space(dev);
+       ret = i915_gem_ring_throttle(dev);
        if (ret)
                return ret;
 

diff --git a/shared-core/i915_drv.h b/shared-core/i915_drv.h
index ef41b43..e3f280d 100644 (file)
--- a/shared-core/i915_drv.h
+++ b/shared-core/i915_drv.h
@@ -331,6 +331,9 @@ struct drm_i915_gem_request {
        /** GEM sequence number associated with this request. */
        uint32_t seqno;
 
+       /** Time at which this request was emitted, in jiffies. */
+       unsigned long emitted_jiffies;
+
        struct list_head list;
 };