fix(runtime): strip inherited jemalloc background thread config for subprocesses

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/main.py

@@ -205,8 +205,8 @@ def run_application() -> None:
     signal.signal(signal.SIGTERM, signal_handler)
     signal.signal(signal.SIGINT, signal_handler)
     # 只在主进程开启分配器后台回收，浏览器等子进程不继承
-    from app.runtime.gc import enable_allocator_background_thread
-    enable_allocator_background_thread()
+    from app.runtime.gc import configure_allocator_background_thread
+    configure_allocator_background_thread()
 
     start_tray()
     run_api_server()

app/runtime/gc.py

@@ -92,6 +92,8 @@ _JEMALLOC_THREAD_TCACHE_FLUSH = b"thread.tcache.flush"
 # 后台回收线程开关与数量上限，均可在运行时写入
 _JEMALLOC_BACKGROUND_THREAD = b"background_thread"
 _JEMALLOC_MAX_BACKGROUND_THREADS = b"max_background_threads"
+# MALLOC_CONF 中与后台线程相关、不能被子进程继承的配置项
+_BACKGROUND_THREAD_OPTIONS = frozenset({"background_thread", "max_background_threads"})
 
 
 @functools.cache
@@ -137,21 +139,25 @@ def flush_thread_allocator_cache() -> bool:
     return mallctl(_JEMALLOC_THREAD_TCACHE_FLUSH, None, None, None, 0) == 0
 
 
-def enable_allocator_background_thread(max_threads: int = 1) -> bool:
+def configure_allocator_background_thread(max_threads: int = 1) -> bool:
     """
-    在当前进程内开启 jemalloc 后台回收线程，按衰减时间把空闲脏页归还系统。
+    让 jemalloc 后台回收线程只在主进程运行，并从子进程将继承的 ``MALLOC_CONF`` 中移除相关项。
 
-    后台线程不能写进 ``MALLOC_CONF``：该环境变量与 ``LD_PRELOAD`` 一起被所有子进程继承，
-    Chromium 的 GPU 进程在后台线程开启时无法启动，浏览器仿真会整体 abort。运行时开启只
-    作用于主进程。用户在 ``MALLOC_CONF`` 中显式配置过后台线程时尊重其选择，不再改写。
+    后台线程按衰减时间把空闲脏页归还系统，但 ``MALLOC_CONF`` 与 ``LD_PRELOAD`` 会被所有子进程
+    继承，Chromium 的 GPU 进程在后台线程开启时无法启动，浏览器仿真整体 abort。
+    - ``MALLOC_CONF`` 已配置后台线程（v3.0.10 镜像默认值或用户显式配置）时，主进程启动时已按其生效，不再改写。
+    - 未配置时通过 ``mallctl`` 在主进程内开启。
+    - 两种情况下都从 ``os.environ`` 中去掉后台线程项。内建更新只替换程序代码、不改镜像环境变量，
+      因此必须由代码清理，才能修复从 v3.0.10 镜像内建更新上来的实例。
 
     Args:
         max_threads: 后台线程上限
 
     Returns:
-        是否实际开启
+        是否在运行时实际开启了后台线程
     """
-    if "background_thread" in os.environ.get("MALLOC_CONF", ""):
+    configured = _strip_background_thread_conf()
+    if configured:
         return False
     mallctl = _jemalloc_mallctl()
     if mallctl is None:
@@ -163,6 +169,22 @@ def enable_allocator_background_thread(max_threads: int = 1) -> bool:
     return mallctl(_JEMALLOC_BACKGROUND_THREAD, None, None, ctypes.byref(enabled), ctypes.sizeof(enabled)) == 0
 
 
+def _strip_background_thread_conf() -> bool:
+    """从 ``os.environ["MALLOC_CONF"]`` 去掉后台线程项，返回原配置是否包含这些项。"""
+    conf = os.environ.get("MALLOC_CONF")
+    if not conf:
+        return False
+    options = [option for option in conf.split(",") if option]
+    kept = [option for option in options if option.split(":", 1)[0] not in _BACKGROUND_THREAD_OPTIONS]
+    if len(kept) == len(options):
+        return False
+    if kept:
+        os.environ["MALLOC_CONF"] = ",".join(kept)
+    else:
+        del os.environ["MALLOC_CONF"]
+    return True
+
+
 def release_allocator_memory() -> Optional[str]:
     """
     把 C 分配器中已释放但尚未归还的空闲页交还操作系统。

tests/test_runtime_allocator_release.py

@@ -149,29 +149,43 @@ def test_thread_cache_flush_is_a_no_op_without_jemalloc(linux, monkeypatch):
     assert trim.calls == []
 
 
+
 def test_background_thread_enabled_at_runtime(linux, monkeypatch):
-    """后台回收线程在主进程内开启，先设上限再打开开关。"""
-    monkeypatch.delenv("MALLOC_CONF", raising=False)
+    """未配置后台线程时在主进程内开启，先设上限再打开开关，子进程环境保持不变。"""
+    monkeypatch.setenv("MALLOC_CONF", "narenas:8,dirty_decay_ms:5000")
     mallctl = _FakeSymbol()
     _use_lib(monkeypatch, _FakeLib(mallctl=mallctl))
 
-    assert runtime_gc.enable_allocator_background_thread() is True
+    assert runtime_gc.configure_allocator_background_thread() is True
     assert [call[0] for call in mallctl.calls] == [b"max_background_threads", b"background_thread"]
     assert all(call[1] is None and call[2] is None for call in mallctl.calls)
+    assert runtime_gc.os.environ["MALLOC_CONF"] == "narenas:8,dirty_decay_ms:5000"
 
 
-def test_background_thread_respects_explicit_malloc_conf(linux, monkeypatch):
-    """用户在 MALLOC_CONF 里显式配置后台线程时不再改写。"""
-    monkeypatch.setenv("MALLOC_CONF", "background_thread:false")
+def test_inherited_background_thread_conf_is_stripped(linux, monkeypatch):
+    """v3.0.10 镜像把后台线程写进了 MALLOC_CONF；主进程已按其生效，只需从子进程将继承的环境中去掉。"""
+    monkeypatch.setenv(
+        "MALLOC_CONF",
+        "background_thread:true,max_background_threads:1,narenas:8,dirty_decay_ms:5000,muzzy_decay_ms:0",
+    )
     mallctl = _FakeSymbol()
     _use_lib(monkeypatch, _FakeLib(mallctl=mallctl))
 
-    assert runtime_gc.enable_allocator_background_thread() is False
+    assert runtime_gc.configure_allocator_background_thread() is False
     assert mallctl.calls == []
+    assert runtime_gc.os.environ["MALLOC_CONF"] == "narenas:8,dirty_decay_ms:5000,muzzy_decay_ms:0"
+
+
+def test_conf_with_only_background_thread_is_removed(linux, monkeypatch):
+    monkeypatch.setenv("MALLOC_CONF", "background_thread:false")
+    _use_lib(monkeypatch, _FakeLib(mallctl=_FakeSymbol()))
+
+    assert runtime_gc.configure_allocator_background_thread() is False
+    assert "MALLOC_CONF" not in runtime_gc.os.environ
 
 
 def test_background_thread_is_a_no_op_without_jemalloc(linux, monkeypatch):
     monkeypatch.delenv("MALLOC_CONF", raising=False)
     _use_lib(monkeypatch, _FakeLib(malloc_trim=_FakeSymbol()))
 
-    assert runtime_gc.enable_allocator_background_thread() is False
+    assert runtime_gc.configure_allocator_background_thread() is False