Teach mojo_benchmark to control caching conditions.

mojo/devtools/common/mojo_benchmark

 #!/usr/bin/env python
 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Runner for Mojo application benchmarks."""
 
 import argparse
 import logging
 import sys
@@ skipping 25 matching lines @@
   - 'avg_duration' - average duration of the targeted event
 
 |benchmark_list_file| may reference the |target_os| global that will be any of
 ['android', 'linux'], indicating the system on which the benchmarks are to be
 run.
 """
 
 _logger = logging.getLogger()
 
 _BENCHMARK_APP = 'https://core.mojoapps.io/benchmark.mojo'
+_CACHE_SERVICE_URL = 'mojo:url_response_disk_cache'
 
 # Additional time in seconds allocated per shell run to accommodate start-up.
 # The shell should terminate before hitting this time out, it is an error if it
 # doesn't.
 _EXTRA_TIMEOUT = 20
 
 
 def _run_benchmark(shell, shell_args, name, app, duration_seconds, measurements,
-                   verbose):
-  """Runs `benchmark.mojo` in a shell with correct arguments, parses and
+                   cold_start, verbose):
+  """Runs `benchmark.mojo` in shell with correct arguments, parses and
   presents the benchmark results.
   """
   timeout = duration_seconds + _EXTRA_TIMEOUT
   benchmark_args = []
   benchmark_args.append('--app=' + app)
   benchmark_args.append('--duration=' + str(duration_seconds))
   for measurement in measurements:
     benchmark_args.append(measurement)
+
+  shell_args = list(shell_args)
   shell_args.append(_BENCHMARK_APP)
   shell_args.append('--args-for=%s %s' % (_BENCHMARK_APP,
                                           ' '.join(benchmark_args)))
+
+  if cold_start:
+    shell_args.append('--args-for=%s %s' % (_CACHE_SERVICE_URL, '--clear'))
+
   if verbose:
     print 'shell arguments: ' + str(shell_args)
-  print '[' + name + ']'
+  print '[ %s ] %s' % (name, 'cold start' if cold_start else 'warm start')
   return_code, output, did_time_out = shell.run_and_get_output(
       shell_args, timeout=timeout)
   output_lines = [line.strip() for line in output.split('\n')]
 
   if return_code or did_time_out or 'benchmark succeeded' not in output_lines:
     print 'timed out' if did_time_out else 'failed'
     if return_code:
       print 'Return code: ' + str(return_code)
     print 'Output: '
     print output
@@ skipping 31 matching lines @@
   benchmark_list = benchmark_list_params['benchmarks']
 
   succeeded = True
   for benchmark_spec in benchmark_list:
     name = benchmark_spec['name']
     app = benchmark_spec['app']
     duration = benchmark_spec['duration']
     shell_args = benchmark_spec.get('shell-args', []) + common_shell_args
     measurements = benchmark_spec['measurements']
     _run_benchmark(shell, shell_args, name, app, duration, measurements,
-                   script_args.verbose)
+                   cold_start=True, verbose=script_args.verbose)
+    _run_benchmark(shell, shell_args, name, app, duration, measurements,
+                   cold_start=False, verbose=script_args.verbose)
 
   return 0 if succeeded else 1
 
 if __name__ == '__main__':
   sys.exit(main())