From edc21cc8ae0eb931de78374223db75a2a4823e7a Mon Sep 17 00:00:00 2001
From: fzyzcjy <5236035+fzyzcjy@users.noreply.github.com>
Date: Sun, 22 Jun 2025 12:40:02 +0800
Subject: [PATCH] Tiny add logging for GC  (#7406)

---
 python/sglang/srt/managers/scheduler.py |  4 ++++
 python/sglang/srt/utils.py              | 25 +++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/python/sglang/srt/managers/scheduler.py b/python/sglang/srt/managers/scheduler.py
index 6dbb75182..34bca70db 100644
--- a/python/sglang/srt/managers/scheduler.py
+++ b/python/sglang/srt/managers/scheduler.py
@@ -140,6 +140,7 @@ from sglang.srt.utils import (
     DeepEPMode,
     DynamicGradMode,
     broadcast_pyobj,
+    configure_gc_logger,
     configure_logger,
     disable_request_logging,
     get_available_gpu_memory,
@@ -508,6 +509,9 @@ class Scheduler(
         )
         self.init_disaggregation()
 
+        if get_bool_env_var("SGLANG_GC_LOG"):
+            configure_gc_logger()
+
     def maybe_sleep_on_idle(self):
         if self.idle_sleeper is not None:
             self.idle_sleeper.maybe_sleep()
diff --git a/python/sglang/srt/utils.py b/python/sglang/srt/utils.py
index 0b3462567..ac8a55442 100644
--- a/python/sglang/srt/utils.py
+++ b/python/sglang/srt/utils.py
@@ -2485,3 +2485,28 @@ def dynamic_import(func_path: str):
     module = importlib.import_module(module_path)
     func = getattr(module, func_name)
     return func
+
+
+def configure_gc_logger():
+    logger.info("Enable GC Logger")
+
+    import gc
+
+    gc_start_time = {}
+
+    def gc_callback(phase, info):
+        gen = info.get("generation", "?")
+        if phase == "start":
+            gc_start_time[gen] = time.time()
+            logger.info(f"GC start: Time {time.time()} | Generation {gen}")
+        elif phase == "stop":
+            duration = time.time() - gc_start_time.get(gen, time.time())
+            collected = info.get("collected", "?")
+            uncollectable = info.get("uncollectable", "?")
+            logger.info(
+                f"GC end: Time {time.time()} | Generation {gen} | "
+                f"Duration: {duration:.4f}s | Collected: {collected} | Uncollectable: {uncollectable} "
+                f'{"(LONG GC)" if duration > 0.1 else ""}'
+            )
+
+    gc.callbacks.append(gc_callback)