wip: minor opt

Author: nascheme

Python/gc_free_threading.c

@@ -973,24 +973,23 @@ move_legacy_finalizer_reachable(struct collection_state *state);
 
 #ifdef GC_ENABLE_MARK_ALIVE
 
-static void
+static bool
 gc_mark_buffer_prime(struct gc_mark_args *args)
 {
-    for (;;) {
-        Py_ssize_t buf_used = args->enqueued - args->dequeued;
-        if (buf_used >= BUFFER_HI) {
-            // When priming, don't fill the buffer since that would
-            // likely cause the stack to be used shortly after when it
-            // fills. We want to use the buffer as much as possible and
-            // so we only fill to BUFFER_HI, not BUFFER_SIZE.
-            return;
-        }
+    // When priming, don't fill the buffer since that would
+    // likely cause the stack to be used shortly after when it
+    // fills. We want to use the buffer as much as possible and
+    // so we only fill to BUFFER_HI, not BUFFER_SIZE.
+    Py_ssize_t space = BUFFER_HI - (args->enqueued - args->dequeued);
+    while (space > 0) {
         PyObject *op = _PyObjectStack_Pop(&args->stack);
         if (op == NULL) {
-            break;
+            return false; // no items left
         }
         gc_mark_buffer_push(op, args);
+        space--;
     }
+    return true;
 }
 
 static int
@@ -1004,8 +1003,7 @@ gc_propagate_alive(struct gc_mark_args *args)
             // the prefetch vs when the object is actually accessed.
             // Prime the buffer with object pointers from the stack,
             // if there are any available.
-            gc_mark_buffer_prime(args);
-            if (args->enqueued == args->dequeued) {
+            if (!gc_mark_buffer_prime(args)) {
                 return 0; // stack and buffer are both empty
             }
         }