iris: Defer closing and freeing VMA until buffers are idle.

There will unfortunately be circumstances where we cannot re-use a
virtual memory address until it's no longer active on the GPU.  To
facilitate this, we instead move BOs to a "dead" list, and defer
closing them and returning their VMA until they are idle.  We
periodically sweep these away in cleanup_bo_cache, which triggers
every time a new object's refcount hits zero.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Tested-by: Jordan Justen <jordan.l.justen@intel.com>

diff --git a/src/gallium/drivers/iris/iris_bufmgr.c b/src/gallium/drivers/iris/iris_bufmgr.c
index da28aad7a753c0d8b3c32b07dbed20f6f11cb97d..d809458240989daf62717bc79d8ffb4ae07ee4a8 100644 (file)
--- a/src/gallium/drivers/iris/iris_bufmgr.c
+++ b/src/gallium/drivers/iris/iris_bufmgr.c
@@ -153,6 +153,12 @@ struct iris_bufmgr {
    struct hash_table *name_table;
    struct hash_table *handle_table;
 
+   /**
+    * List of BOs which we've effectively freed, but are hanging on to
+    * until they're idle before closing and returning the VMA.
+    */
+   struct list_head zombie_list;
+
    struct util_vma_heap vma_allocator[IRIS_MEMZONE_COUNT];
 
    bool has_llc:1;
@@ -700,6 +706,25 @@ err_unref:
    return NULL;
 }
 
+static void
+bo_close(struct iris_bo *bo)
+{
+   struct iris_bufmgr *bufmgr = bo->bufmgr;
+
+   /* Close this object */
+   struct drm_gem_close close = { .handle = bo->gem_handle };
+   int ret = drm_ioctl(bufmgr->fd, DRM_IOCTL_GEM_CLOSE, &close);
+   if (ret != 0) {
+      DBG("DRM_IOCTL_GEM_CLOSE %d failed (%s): %s\n",
+          bo->gem_handle, bo->name, strerror(errno));
+   }
+
+   /* Return the VMA for reuse */
+   vma_free(bo->bufmgr, bo->gtt_offset, bo->size);
+
+   free(bo);
+}
+
 static void
 bo_free(struct iris_bo *bo)
 {
@@ -730,17 +755,14 @@ bo_free(struct iris_bo *bo)
       _mesa_hash_table_remove(bufmgr->handle_table, entry);
    }
 
-   /* Close this object */
-   struct drm_gem_close close = { .handle = bo->gem_handle };
-   int ret = drm_ioctl(bufmgr->fd, DRM_IOCTL_GEM_CLOSE, &close);
-   if (ret != 0) {
-      DBG("DRM_IOCTL_GEM_CLOSE %d failed (%s): %s\n",
-          bo->gem_handle, bo->name, strerror(errno));
+   if (bo->idle) {
+      bo_close(bo);
+   } else {
+      /* Defer closing the GEM BO and returning the VMA for reuse until the
+       * BO is idle.  Just move it to the dead list for now.
+       */
+      list_addtail(&bo->head, &bufmgr->zombie_list);
    }
-
-   vma_free(bo->bufmgr, bo->gtt_offset, bo->size);
-
-   free(bo);
 }
 
 /** Frees all cached buffers significantly older than @time. */
@@ -765,6 +787,17 @@ cleanup_bo_cache(struct iris_bufmgr *bufmgr, time_t time)
       }
    }
 
+   list_for_each_entry_safe(struct iris_bo, bo, &bufmgr->zombie_list, head) {
+      /* Stop once we reach a busy BO - all others past this point were
+       * freed more recently so are likely also busy.
+       */
+      if (!bo->idle && iris_bo_busy(bo))
+         break;
+
+      list_del(&bo->head);
+      bo_close(bo);
+   }
+
    bufmgr->time = time;
 }
 
@@ -1177,6 +1210,12 @@ iris_bufmgr_destroy(struct iris_bufmgr *bufmgr)
       }
    }
 
+   /* Close any buffer objects on the dead list. */
+   list_for_each_entry_safe(struct iris_bo, bo, &bufmgr->zombie_list, head) {
+      list_del(&bo->head);
+      bo_close(bo);
+   }
+
    _mesa_hash_table_destroy(bufmgr->name_table, NULL);
    _mesa_hash_table_destroy(bufmgr->handle_table, NULL);
 
@@ -1563,6 +1602,8 @@ iris_bufmgr_init(struct gen_device_info *devinfo, int fd)
       return NULL;
    }
 
+   list_inithead(&bufmgr->zombie_list);
+
    bufmgr->has_llc = devinfo->has_llc;
 
    STATIC_ASSERT(IRIS_MEMZONE_SHADER_START == 0ull);