[Core] GC Debug callback (#24829)

Signed-off-by: Jialin Ouyang <jialino@meta.com>
Signed-off-by: Jialin Ouyang <Jialin.Ouyang@gmail.com>
Co-authored-by: Jialin Ouyang <jialino@meta.com>

vllm/v1/engine/core.py

@@ -29,6 +29,7 @@ from vllm.transformers_utils.config import (
     maybe_register_config_serialize_by_value)
 from vllm.utils import (decorate_logs, get_hash_fn_by_name, make_zmq_socket,
                         resolve_obj_by_qualname, set_process_title)
+from vllm.utils.gc_utils import maybe_attach_gc_debug_callback
 from vllm.v1.core.kv_cache_utils import (BlockHash,
                                          generate_scheduler_kv_cache_config,
                                          get_kv_cache_configs,
@@ -532,6 +533,9 @@ class EngineCoreProc(EngineCore):
         gc.collect()
         gc.freeze()
 
+        # If enable, attach GC debugger after static variable freeze.
+        maybe_attach_gc_debug_callback()
+
     @contextmanager
     def _perform_handshakes(
         self,