Android perf tests: only store the retry results if it's better.

Rather than blindingly store the results of the latest perf test,
keep the "least worst" run.

BUG=

Review URL: https://codereview.chromium.org/27502002

git-svn-id: http://src.chromium.org/svn/trunk/src/build@229351 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

android/pylib/perf/setup.py

@@ -10,6 +10,7 @@ import logging
 import os
 import psutil
 import signal
+import shutil
 import time
 
 from pylib import android_commands
@@ -58,7 +59,8 @@ def Setup(test_options):
   Returns:
     A tuple of (TestRunnerFactory, tests).
   """
-  if not os.path.exists(constants.PERF_OUTPUT_DIR):
+  if os.path.exists(constants.PERF_OUTPUT_DIR):
+    shutil.rmtree(constants.PERF_OUTPUT_DIR)
   os.makedirs(constants.PERF_OUTPUT_DIR)
 
   # Before running the tests, kill any leftover server.

android/pylib/perf/test_runner.py

@@ -2,7 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-"""Runs a perf test on a single device.
+"""Runs perf tests.
 
 Our buildbot infrastructure requires each slave to run steps serially.
 This is sub-optimal for android, where these steps can run independently on
@@ -93,8 +93,21 @@ class TestRunner(base_test_runner.BaseTestRunner):
     self._tests = tests
     self._flaky_tests = flaky_tests
 
+  @staticmethod
+  def _IsBetter(result):
+    if result['actual_exit_code'] == 0:
+      return True
+    pickled = os.path.join(constants.PERF_OUTPUT_DIR,
+                           result['name'])
+    if not os.path.exists(pickled):
+      return True
+    with file(pickled, 'r') as f:
+      previous = pickle.loads(f.read())
+    return result['actual_exit_code'] < previous['actual_exit_code']
+
   @staticmethod
   def _SaveResult(result):
+    if TestRunner._IsBetter(result):
       with file(os.path.join(constants.PERF_OUTPUT_DIR,
                              result['name']), 'w') as f:
         f.write(pickle.dumps(result))
@@ -133,6 +146,7 @@ class TestRunner(base_test_runner.BaseTestRunner):
     result_type = base_test_result.ResultType.FAIL
     if exit_code == 0:
       result_type = base_test_result.ResultType.PASS
+    actual_exit_code = exit_code
     if test_name in self._flaky_tests:
       # The exit_code is used at the second stage when printing the
       # test output. If the test is flaky, force to "0" to get that step green
@@ -144,6 +158,7 @@ class TestRunner(base_test_runner.BaseTestRunner):
         'name': test_name,
         'output': output,
         'exit_code': exit_code,
+        'actual_exit_code': actual_exit_code,
         'result_type': result_type,
         'total_time': (end_time - start_time).seconds,
         'device': self.device,