util/u_queue: add an option to set the minimum thread priority

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>

src/gallium/auxiliary/util/u_threaded_context.c

@@ -2203,7 +2203,7 @@ threaded_context_create(struct pipe_context *pipe,
     * from the queue before being executed, so keep one tc_batch slot for that
     * execution. Also, keep one unused slot for an unflushed batch.
     */
-   if (!util_queue_init(&tc->queue, "gallium_drv", TC_MAX_BATCHES - 2, 1))
+   if (!util_queue_init(&tc->queue, "gallium_drv", TC_MAX_BATCHES - 2, 1, 0))
       goto fail;
 
    for (unsigned i = 0; i < TC_MAX_BATCHES; i++) {

src/gallium/drivers/freedreno/freedreno_batch.c

@@ -276,7 +276,7 @@ batch_flush(struct fd_batch *batch)
 		fd_batch_reference(&tmp, batch);
 
 		if (!util_queue_is_initialized(&batch->ctx->flush_queue))
-			util_queue_init(&batch->ctx->flush_queue, "flush_queue", 16, 1);
+			util_queue_init(&batch->ctx->flush_queue, "flush_queue", 16, 1, 0);
 
 		util_queue_add_job(&batch->ctx->flush_queue,
 				batch, &batch->flush_fence,

src/gallium/drivers/radeonsi/si_pipe.c

@@ -890,7 +890,7 @@ struct pipe_screen *radeonsi_screen_create(struct radeon_winsys *ws)
 	num_compiler_threads = MIN2(num_cpus, ARRAY_SIZE(sscreen->tm));
 
 	if (!util_queue_init(&sscreen->shader_compiler_queue, "si_shader",
-			     32, num_compiler_threads)) {
+			     32, num_compiler_threads, 0)) {
 		si_destroy_shader_cache(sscreen);
 		FREE(sscreen);
 		return NULL;

src/gallium/winsys/amdgpu/drm/amdgpu_winsys.c

@@ -305,7 +305,7 @@ amdgpu_winsys_create(int fd, radeon_screen_create_t screen_create)
    (void) mtx_init(&ws->global_bo_list_lock, mtx_plain);
    (void) mtx_init(&ws->bo_fence_lock, mtx_plain);
 
-   if (!util_queue_init(&ws->cs_queue, "amdgpu_cs", 8, 1)) {
+   if (!util_queue_init(&ws->cs_queue, "amdgpu_cs", 8, 1, 0)) {
       amdgpu_winsys_destroy(&ws->base);
       mtx_unlock(&dev_tab_mutex);
       return NULL;

src/gallium/winsys/radeon/drm/radeon_drm_winsys.c

@@ -821,7 +821,7 @@ radeon_drm_winsys_create(int fd, radeon_screen_create_t screen_create)
     ws->info.gart_page_size = sysconf(_SC_PAGESIZE);
 
     if (ws->num_cpus > 1 && debug_get_option_thread())
-        util_queue_init(&ws->cs_queue, "radeon_cs", 8, 1);
+        util_queue_init(&ws->cs_queue, "radeon_cs", 8, 1, 0);
 
     /* Create the screen at the end. The winsys must be initialized
      * completely.

src/util/disk_cache.c

@@ -342,7 +342,7 @@ disk_cache_create(const char *gpu_name, const char *timestamp,
     * really care about getting things to disk quickly just that it's not
     * blocking other tasks.
     */
-   util_queue_init(&cache->cache_queue, "disk_cache", 32, 1);
+   util_queue_init(&cache->cache_queue, "disk_cache", 32, 1, 0);
 
    /* Create driver id keys */
    size_t ts_size = strlen(timestamp) + 1;

src/util/u_queue.c

@@ -147,6 +147,21 @@ util_queue_thread_func(void *input)
       u_thread_setname(name);
    }
 
+   if (queue->flags & UTIL_QUEUE_INIT_USE_MINIMUM_PRIORITY) {
+#if defined(__linux__)
+      struct sched_param sched_param = {0};
+
+      /* The nice() function can only set a maximum of 19.
+       * SCHED_IDLE is the same as nice = 20.
+       *
+       * Note that Linux only allows decreasing the priority. The original
+       * priority can't be restored.
+       */
+      pthread_setschedparam(queue->threads[thread_index], SCHED_IDLE,
+                            &sched_param);
+#endif
+   }
+
    while (1) {
       struct util_queue_job job;
 
@@ -197,13 +212,15 @@ bool
 util_queue_init(struct util_queue *queue,
                 const char *name,
                 unsigned max_jobs,
-                unsigned num_threads)
+                unsigned num_threads,
+                unsigned flags)
 {
    unsigned i;
 
    memset(queue, 0, sizeof(*queue));
    queue->name = name;
    queue->num_threads = num_threads;
+   queue->flags = flags;
    queue->max_jobs = max_jobs;
 
    queue->jobs = (struct util_queue_job*)

src/util/u_queue.h

@@ -42,6 +42,8 @@
 extern "C" {
 #endif
 
+#define UTIL_QUEUE_INIT_USE_MINIMUM_PRIORITY      (1 << 0)
+
 /* Job completion fence.
  * Put this into your job structure.
  */
@@ -69,6 +71,7 @@ struct util_queue {
    thrd_t *threads;
    int num_queued;
    unsigned num_threads;
+   unsigned flags;
    int kill_threads;
    int max_jobs;
    int write_idx, read_idx; /* ring buffer pointers */
@@ -81,7 +84,8 @@ struct util_queue {
 bool util_queue_init(struct util_queue *queue,
                      const char *name,
                      unsigned max_jobs,
-                     unsigned num_threads);
+                     unsigned num_threads,
+                     unsigned flags);
 void util_queue_destroy(struct util_queue *queue);
 void util_queue_fence_init(struct util_queue_fence *fence);
 void util_queue_fence_destroy(struct util_queue_fence *fence);