Bug 1271448 - Stop saving reftest.log for |mach reftest| perf improvements, r?jgraham In bug 1271035 gps identified disk I/O as a major cause for reftest slowness. He was able to fix most of it, but the new highest source of I/O in reftest is reftest.log. To note, we were only saving reftest.log when running via mach, so this won't impact automation in any way: https://hg.mozilla.org/mozilla-central/file/043082cb7bd8/layout/tools/reftest/mach_commands.py#l204 I don't know why we are doing this given that the same output goes to stdout. And as dholbert pointed out, since bug 1034290 landed, that log contains raw structured logs, which are not at all useful for debugging. Given that it is no longer useful and causes slowness, we should stop saving it. If anyone wishes to keep saving to a log, they can use: ./mach reftest --log-tbpl reftest.log If they wish this to be the default behaviour they can make a machrc (or .machrc) in either topsrcdir, ~/.mozbuild or $MACHRC. Then add: [alias] reftest = reftest --log-tbpl reftest.log MozReview-Commit-ID: A3e2X7qF90H

--- a/layout/tools/reftest/mach_commands.py
+++ b/layout/tools/reftest/mach_commands.py
@@ -195,19 +195,16 @@ class ReftestRunner(MozbuildObject):
         if not kwargs["tests"]:
             kwargs["tests"] = [os.path.join(*default_manifest[kwargs["suite"]])]
 
         if kwargs["suite"] == "jstestbrowser":
             kwargs["extraProfileFiles"].append(os.path.join(self.topobjdir, "dist",
                                                             "test-stage", "jsreftest",
                                                             "tests", "user.js"))
 
-        if not kwargs["runTestsInParallel"]:
-            kwargs["logFile"] = "%s.log" % kwargs["suite"]
-
         self.log_manager.enable_unstructured()
         try:
             rv = runreftest.run(**kwargs)
         finally:
             self.log_manager.disable_unstructured()
 
         return rv