experiment with starting the threadpool at size 1

jcupitt · jcupitt · commit c83988317c6f · 2025-12-31T19:12:33.000Z
We currently start threadpools at 50% of max size and let them expand
and contract with load. Since this happens pretty quickly, how about
starting threadpools at size 1 instead? Simple pipelines would be
quicker, heavy pipelines would hardly slow down.

Trivial patch for experimentation.
diff --git a/libvips/iofuncs/threadpool.c b/libvips/iofuncs/threadpool.c
@@ -647,10 +647,11 @@ vips_threadpool_run(VipsImage *im,
 	pool->work = work;
 	pool->a = a;
 
-	/* Start with half of the max number of threads, then let it drift up
+	/* Start with a single thread, then let it drift up
 	 * and down with load.
 	 */
 	for (n_working = 0; n_working < 1 + pool->max_workers / 2; n_working++)
+	// for (n_working = 0; n_working < 1; n_working++)
 		if (vips_worker_new(pool)) {
 			vips_threadpool_free(pool);
 			return -1;
