From e41a0fa3772c5b9bbca439ce5ed7d05803febbc1 Mon Sep 17 00:00:00 2001
From: Nick Hill <nhill@redhat.com>
Date: Thu, 4 Sep 2025 07:55:23 -0700
Subject: [PATCH] [Perf] Freeze core engine proc heap after init (#24008)

Signed-off-by: Nick Hill <nhill@redhat.com>
---
 vllm/v1/engine/core.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/vllm/v1/engine/core.py b/vllm/v1/engine/core.py
index 922c06b44be..d7e9cfa3660 100644
--- a/vllm/v1/engine/core.py
+++ b/vllm/v1/engine/core.py
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+import gc
 import os
 import queue
 import signal
@@ -536,6 +537,11 @@ class EngineCoreProc(EngineCore):
         self.step_fn = (self.step if self.batch_queue is None else
                         self.step_with_batch_queue)
 
+        # Mark the startup heap as static so that it's ignored by GC.
+        # Reduces pause times of oldest generation collections.
+        gc.collect()
+        gc.freeze()
+
     @contextmanager
     def _perform_handshakes(
         self,