Add Greed Work Stealing and Random Load Balancing for check_procedure_bodies

src/checker.cpp

@@ -4554,33 +4554,59 @@ bool consume_proc_info_queue(Checker *c, ProcInfo *pi, ProcBodyQueue *q, Untyped
 struct ThreadProcBodyData {
 	Checker *checker;
 	ProcBodyQueue *queue;
-	isize thread_index;
+	u32 thread_index;
+	u32 thread_count;
 	ThreadProcBodyData *all_data;
-	isize thread_count;
 };
 
 GB_THREAD_PROC(thread_proc_body) {
 	ThreadProcBodyData *data = cast(ThreadProcBodyData *)thread->user_data;
 	Checker *c = data->checker;
-	ProcBodyQueue *q = data->queue;
+	ThreadProcBodyData *all_data = data->all_data;
-	ProcInfo *pi = nullptr;
+	ProcBodyQueue *this_queue = data->queue;
 
 	UntypedExprInfoMap untyped = {};
 	map_init(&untyped, heap_allocator());
 	defer (map_destroy(&untyped));
 
-	while (mpmc_dequeue(q, &pi)) {
+	gbRandom r = {}; gb_random_init(&r);
+
+	for (ProcInfo *pi; mpmc_dequeue(this_queue, &pi); /**/) {
+		// NOTE(bill): Randomize the load balancing of procs
+		// adding more procs to the queues
+		u32 index = gb_random_gen_u32(&r) % data->thread_count;
+		ProcBodyQueue *q = all_data[index].queue;
 		consume_proc_info_queue(c, pi, q, &untyped);
 	}
 
+	// Greedy Work Stealing
+retry:;
+	isize max_count = 0;
+	isize best_index = -1;
+	for (u32 i = 0; i < data->thread_count; i++) {
+		ProcBodyQueue *q = all_data[i].queue;
+		isize count = q->count.load(std::memory_order_relaxed);
+		if (max_count < count)  {
+			max_count = count;
+			best_index = i;
+		}
+	}
+	if (best_index >= 0) {
+		ProcBodyQueue *other_queue = all_data[best_index].queue;
+		for (ProcInfo *pi; mpmc_dequeue(other_queue, &pi); /**/) {
+			consume_proc_info_queue(c, pi, this_queue, &untyped);
+		}
+		goto retry;
+	}
+
 	gb_semaphore_release(&c->procs_to_check_semaphore);
 
 	return 0;
 }
 
 void check_procedure_bodies(Checker *c) {
-	isize thread_count = gb_max(build_context.thread_count, 1);
+	u32 thread_count = cast(u32)gb_max(build_context.thread_count, 1);
-	isize worker_count = thread_count-1; // NOTE(bill): The main thread will also be used for work
+	u32 worker_count = thread_count-1; // NOTE(bill): The main thread will also be used for work
 	if (!build_context.threaded_checker) {
 		worker_count = 0;
 
@@ -4600,13 +4626,13 @@ void check_procedure_bodies(Checker *c) {
 	isize load_count = (original_queue_count+thread_count-1)/thread_count;
 
 	ThreadProcBodyData *thread_data = gb_alloc_array(permanent_allocator(), ThreadProcBodyData, thread_count);
-	for (isize i = 0; i < thread_count; i++) {
+	for (u32 i = 0; i < thread_count; i++) {
 		ThreadProcBodyData *data = thread_data + i;
 		data->checker = c;
 		data->queue = gb_alloc_item(permanent_allocator(), ProcBodyQueue);
 		data->thread_index = i;
-		data->all_data = data;
 		data->thread_count = thread_count;
+		data->all_data = thread_data;
 		// NOTE(bill) 2x the amount assumes on average only 1 nested procedure
 		// TODO(bill): Determine a good heuristic
 		mpmc_init(data->queue, heap_allocator(), next_pow2_isize(load_count*2));