process replay: create openpilot prefix directories once (#35864)

this is so slow

common/prefix.py

@@ -9,20 +9,19 @@ from openpilot.system.hardware.hw import Paths
 from openpilot.system.hardware.hw import DEFAULT_DOWNLOAD_CACHE_ROOT
 
 class OpenpilotPrefix:
-  def __init__(self, prefix: str = None, clean_dirs_on_exit: bool = True, shared_download_cache: bool = False):
+  def __init__(self, prefix: str = None, create_dirs_on_enter: bool = True, clean_dirs_on_exit: bool = True, shared_download_cache: bool = False):
     self.prefix = prefix if prefix else str(uuid.uuid4().hex[0:15])
     self.msgq_path = os.path.join(Paths.shm_path(), self.prefix)
+    self.create_dirs_on_enter = create_dirs_on_enter
     self.clean_dirs_on_exit = clean_dirs_on_exit
     self.shared_download_cache = shared_download_cache
 
   def __enter__(self):
     self.original_prefix = os.environ.get('OPENPILOT_PREFIX', None)
     os.environ['OPENPILOT_PREFIX'] = self.prefix
-    try:
-      os.mkdir(self.msgq_path)
-    except FileExistsError:
-      pass
-    os.makedirs(Paths.log_root(), exist_ok=True)
+
+    if self.create_dirs_on_enter:
+      self.create_dirs()
 
     if self.shared_download_cache:
       os.environ["COMMA_CACHE"] = DEFAULT_DOWNLOAD_CACHE_ROOT
@@ -40,6 +39,13 @@ class OpenpilotPrefix:
       pass
     return False
 
+  def create_dirs(self):
+    try:
+      os.mkdir(self.msgq_path)
+    except FileExistsError:
+      pass
+    os.makedirs(Paths.log_root(), exist_ok=True)
+
   def clean_dirs(self):
     symlink_path = Params().get_param_path()
     if os.path.exists(symlink_path):

selfdrive/test/process_replay/process_replay.py

@@ -147,7 +147,7 @@ class ProcessConfig:
 
 class ProcessContainer:
   def __init__(self, cfg: ProcessConfig):
-    self.prefix = OpenpilotPrefix(clean_dirs_on_exit=False)
+    self.prefix = OpenpilotPrefix(create_dirs_on_enter=False, clean_dirs_on_exit=False)
     self.cfg = copy.deepcopy(cfg)
     self.process = copy.deepcopy(managed_processes[cfg.proc_name])
     self.msg_queue: list[capnp._DynamicStructReader] = []
@@ -229,6 +229,7 @@ class ProcessContainer:
     fingerprint: str | None, capture_output: bool
   ):
     with self.prefix as p:
+      self.prefix.create_dirs()
       self._setup_env(params_config, environ_config)
 
       if self.cfg.config_callback is not None: