zink: add a binary semaphore cache

after being waited upon, a binary semaphore can be reused, which saves
tons of present-related ioctls when fps is high

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20681>

src/gallium/drivers/zink/zink_batch.c

@@ -198,8 +198,13 @@ unref_resources(struct zink_screen *screen, struct zink_batch_state *bs)
       /* this is typically where resource objects get destroyed */
       zink_resource_object_reference(screen, &obj, NULL);
    }
-   while (util_dynarray_contains(&bs->unref_semaphores, VkSemaphore))
-      VKSCR(DestroySemaphore)(screen->dev, util_dynarray_pop(&bs->unref_semaphores, VkSemaphore), NULL);
+   /* check the arrays first to avoid locking unnecessarily */
+   if (!util_dynarray_contains(&bs->unref_semaphores, VkSemaphore))
+      return;
+   simple_mtx_lock(&screen->semaphores_lock);
+   util_dynarray_append_dynarray(&screen->semaphores, &bs->unref_semaphores);
+   util_dynarray_clear(&bs->unref_semaphores);
+   simple_mtx_unlock(&screen->semaphores_lock);
 }
 
 /* utility for resetting a batch state; called on context destruction */

src/gallium/drivers/zink/zink_screen.c

@@ -1434,6 +1434,10 @@ zink_destroy_screen(struct pipe_screen *pscreen)
    if (screen->threaded)
       util_queue_destroy(&screen->flush_queue);
 
+   simple_mtx_destroy(&screen->semaphores_lock);
+   while (util_dynarray_contains(&screen->semaphores, VkSemaphore))
+      VKSCR(DestroySemaphore)(screen->dev, util_dynarray_pop(&screen->semaphores, VkSemaphore), NULL);
+
    simple_mtx_destroy(&screen->queue_lock);
    VKSCR(DestroyDevice)(screen->dev, NULL);
    VKSCR(DestroyInstance)(screen->instance, NULL);
@@ -2520,6 +2524,14 @@ zink_create_semaphore(struct zink_screen *screen)
       0
    };
    VkSemaphore sem = VK_NULL_HANDLE;
+   if (util_dynarray_contains(&screen->semaphores, VkSemaphore)) {
+      simple_mtx_lock(&screen->semaphores_lock);
+      if (util_dynarray_contains(&screen->semaphores, VkSemaphore))
+         sem = util_dynarray_pop(&screen->semaphores, VkSemaphore);
+      simple_mtx_unlock(&screen->semaphores_lock);
+   }
+   if (sem)
+      return sem;
    VkResult ret = VKSCR(CreateSemaphore)(screen->dev, &sci, NULL, &sem);
    return ret == VK_SUCCESS ? sem : VK_NULL_HANDLE;
 }
@@ -2830,6 +2842,9 @@ zink_internal_create_screen(const struct pipe_screen_config *config)
 
    util_idalloc_mt_init_tc(&screen->buffer_ids);
 
+   simple_mtx_init(&screen->semaphores_lock, mtx_plain);
+   util_dynarray_init(&screen->semaphores, screen);
+
    util_vertex_state_cache_init(&screen->vertex_state_cache,
                                 zink_create_vertex_state, zink_vertex_state_destroy);
    screen->base.create_vertex_state = zink_cache_create_vertex_state;

src/gallium/drivers/zink/zink_types.h

@@ -1226,6 +1226,9 @@ struct zink_screen {
    struct util_queue flush_queue;
    struct zink_context *copy_context;
 
+   simple_mtx_t semaphores_lock;
+   struct util_dynarray semaphores;
+
    unsigned buffer_rebind_counter;
    unsigned image_rebind_counter;
    unsigned robust_ctx_count;