speed up log writing

old-commit-hash: f728edfd03

selfdrive/test/process_replay/compare_logs.py

@@ -16,10 +16,10 @@ from tools.lib.logreader import LogReader
 EPSILON = sys.float_info.epsilon
 
 
-def save_log(dest, log_msgs):
-  dat = b""
-  for msg in tqdm(log_msgs):
-    dat += msg.as_builder().to_bytes()
+def save_log(dest, log_msgs, compress=True):
+  dat = b"".join([msg.as_builder().to_bytes() for msg in tqdm(log_msgs)])
+
+  if compress:
     dat = bz2.compress(dat)
 
   with open(dest, "wb") as f: