tools: Local tests for the speculative prefetch predictor.

tools/resource_prefetch_predictor/prefetch_benchmark.py

+#!/usr/bin/python

[pasko, 2016/11/17 15:59:04]

every time I get a review in tools/resource_prefetch_predictor I get reminded
that a better place for this is in chrome/browser/predictors/tools, but afraid
to cause too many conflicts for you. Can you do it at a point that is
comfortable for you? Thanks :)

[Benoit L, 2016/11/21 13:40:32]

Acknowledged.

+#
+# Copyright 2016 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.
+
+"""Loads a web page with speculative prefetch, and collects loading metrics."""
+
+import argparse
+import logging
+import os
+import sys
+import time
+
+_SRC_PATH = os.path.abspath(os.path.join(
+    os.path.dirname(__file__), os.pardir, os.pardir))
+
+sys.path.append(os.path.join(
+    _SRC_PATH, 'tools', 'android', 'customtabs_benchmark', 'scripts'))
+import customtabs_benchmark
+
+sys.path.append(os.path.join(_SRC_PATH, 'tools', 'android', 'loading'))
+from options import OPTIONS
+
+sys.path.append(os.path.join(_SRC_PATH, 'build', 'android'))
+import devil_chromium
+
+sys.path.append(os.path.join(_SRC_PATH, 'third_party', 'catapult', 'devil'))
+from devil.android.sdk import intent
+
+import common
+
+
+def _CreateArgumentParser():
+  """Creates and returns the argument parser."""
+  parser = common.CreateBaseArgumentParser(
+      'Loads a URL with prefetch and prints loading metrics.')

[pasko, 2016/11/17 15:59:04]

s/prefetch/resource_prefetch_predictor/ would be better understood by other
teams

[Benoit L, 2016/11/21 13:40:32]

Done.

+  parser.add_argument('--device', help='Device ID')
+  parser.add_argument('--database',
+                      help=('File containing the predictor database, as '
+                            'obtained from generate_database.py.'))
+  parser.add_argument('--url', help='URL to load.')
+  parser.add_argument('--prefetch_delay_ms',
+                      help='Prefetch delay in ms. -1 to disable prefetch.')
+  return parser
+
+
+def _Setup(device, database_filename):
+  """Sets up a device and returns an instance of RemoteChromeController."""
+  chrome_controller = common.Setup(device, [''])
+  chrome_package = OPTIONS.ChromePackage()
+  device.ForceStop(chrome_package.package)
+  chrome_controller.ResetBrowserState()
+  # Launch Chrome a first time to recreate the local state.

[pasko, 2016/11/17 15:59:04]

nit: s/a/for the/

[Benoit L, 2016/11/21 13:40:32]

Done.

+  launch_intent = intent.Intent(
+      action='android.intent.action.MAIN',
+      package=chrome_package.package,
+      activity=chrome_package.activity)
+  device.StartActivity(launch_intent, blocking=True)
+  time.sleep(5)
+  device.ForceStop(chrome_package.package)
+  # Now push the database. Needs to be done after the first launch, otherwise
+  # the profile directory is owned by root.

[pasko, 2016/11/17 15:59:04]

What ensures that Chrome creates the database? I am worried that Chrome may
start, but the db file is not created .. the file will be later owned by root
and Chrome would not be able to update it.

[Benoit L, 2016/11/21 13:40:32]

Good catch, thanks!

Done.

+  database_content = open(database_filename, 'r').read()
+  device.WriteFile(common.DatabaseDevicePath(), database_content,
+                   force_push=True)
+
+
+def _Go(device, url, prefetch_delay_ms):
+  disable_prefetch = prefetch_delay_ms == -1
+  chrome_args = (customtabs_benchmark.CHROME_ARGS
+                 + ['--trace-startup', '--trace-startup-duration=20'])
+  if not disable_prefetch:
+    chrome_args.append('--speculative-resource-prefetching=enabled')
+  prefetch_mode = 'disabled' if disable_prefetch else 'speculative_prefetch'
+  result = customtabs_benchmark.RunOnce(
+      device, url, True, prefetch_mode, 2000, max(0, prefetch_delay_ms), False,
+      chrome_args, False)

[pasko, 2016/11/17 15:59:04]

this function has quite a few parameters, maintaining the right order is
error-prone, better pass with parameter names.

[Benoit L, 2016/11/21 13:40:32]

Done.

+  print customtabs_benchmark.ParseResult(result)
+
+
+def main():
+  devil_chromium.Initialize()
+  logging.basicConfig(level=logging.INFO)

[pasko, 2016/11/17 15:59:04]

setting up logging before initialization of an external component would be more
debuggable, so unless it spits too much currently please do it

[Benoit L, 2016/11/21 13:40:32]

Done.

+
+  parser = _CreateArgumentParser()
+  args = common.ParseAndReturnArgs(parser)
+  device = common.FindDevice(args.device)
+  if device is None:
+    logging.error('Could not find device: %s.', args.device)
+    sys.exit(1)
+
+  _Setup(device, args.database)
+  _Go(device, args.url, int(args.prefetch_delay_ms))
+
+
+if __name__ == '__main__':
+  main()