[Memory] Retire graph borrow pool before updating static runs (#37966)

Co-authored-by: Shiyan Deng <dsy842974287@meta.com>

python/sglang/srt/model_executor/runner_utils/pool.py

@@ -58,9 +58,11 @@ def set_graph_pool_borrow_runs(runs: list[tuple[int, int]]) -> None:
     borrowing.
     """
     global _borrow_static_runs
-    _borrow_static_runs = sorted(runs, key=lambda run: run[1], reverse=True)[
+    static_runs = sorted(runs, key=lambda run: run[1], reverse=True)[
         : BumpArenaStub.MAX_EXTENTS
     ]
+    _teardown_borrow_pool()
+    _borrow_static_runs = static_runs
     logger.info(
         "Graph pool borrow runs pinned: runs=%d free=%d",
         len(_borrow_static_runs),

test/registered/unit/model_executor/runner_utils/test_graph_pool_borrow.py

@@ -122,6 +122,20 @@ class TestGraphPoolBorrow(CustomTestCase):
             pool.disable_graph_pool_borrow("graph storage is externally managed")
             self.assertFalse(pool.graph_pool_borrow_enabled())
 
+    def test_setting_static_runs_retires_previous_borrow_pool(self):
+        runs = [(0x1000, 4096), (0x2000, 8192)]
+
+        def reset_static_runs():
+            pool._borrow_static_runs = None
+
+        with patch.object(
+            pool, "_teardown_borrow_pool", side_effect=reset_static_runs
+        ) as teardown:
+            pool.set_graph_pool_borrow_runs(runs)
+
+        teardown.assert_called_once_with()
+        self.assertEqual(pool._borrow_static_runs, [(0x2000, 8192), (0x1000, 4096)])
+
     def test_eagle_non_greedy_probabilities_do_not_borrow_graph_pool(self):
         def fake_sampling(**kwargs):
             kwargs["predicts"].fill_(3)