tools/perf/profile_creators/history_profile_extender.py

   1 # Copyright 2015 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4 import multiprocessing
   5 import os
   6 import tempfile
   7
   8 from profile_creators import fast_navigation_profile_extender
   9
  10
  11 class HistoryProfileExtender(
  12     fast_navigation_profile_extender.FastNavigationProfileExtender):
  13   """This extender navigates Chrome to a large number of URIs pointing to local
  14   files. It continues running until the history DB becomes full."""
  15   _HISTORY_DB_MAX_SIZE_IN_MB = 10
  16
  17   def __init__(self):
  18     # The rate limiting factors are the speed of page navigation, and the speed
  19     # of python bindings. The former is larger than the latter, so having a
  20     # large batch size skews the amortized average time per page load towards
  21     # the latter.
  22     maximum_batch_size = multiprocessing.cpu_count() * 2
  23     super(HistoryProfileExtender, self).__init__(maximum_batch_size)
  24
  25     # A list of paths of temporary files. The instance is responsible for
  26     # making sure that the files are deleted before they are removed from this
  27     # list.
  28     self._generated_temp_files = []
  29
  30   def _MakeTemporaryFile(self):
  31     """Makes a temporary file and returns a URI to the file.
  32
  33     This method has the side effect of appending the temporary file to
  34     self._generated_temp_files. The instance is responsible for deleting the
  35     file at a later point in time.
  36     """
  37     # Adding a long suffix to the name of the file fills up the history
  38     # database faster. The suffix can't be too long, since some file systems
  39     # have a 256 character limit on the length of the path. While we could
  40     # dynamically vary the length of the path, that would generate different
  41     # profiles on different OSes, which is not ideal.
  42     suffix = "reallylongsuffixintendedtoartificiallyincreasethelengthoftheurl"
  43
  44     # Neither tempfile.TemporaryFile() nor tempfile.NamedTemporaryFile() work
  45     # well here. The former doesn't work at all, since it doesn't gaurantee a
  46     # file-system visible path. The latter doesn't work well, since the
  47     # returned file cannot be opened a second time on Windows. The returned
  48     # file would have to be closed, and the method would need to be called with
  49     # Delete=False, which makes its functionality no simpler than
  50     # tempfile.mkstemp().
  51     handle, path = tempfile.mkstemp(suffix=suffix)
  52     os.close(handle)
  53     self._generated_temp_files.append(path)
  54
  55     file_url = "file://" + path
  56     return file_url
  57
  58   def GetUrlIterator(self):
  59     """Superclass override."""
  60     while True:
  61       yield self._MakeTemporaryFile()
  62
  63   def ShouldExitAfterBatchNavigation(self):
  64     """Superclass override."""
  65     return self._IsHistoryDBAtMaxSize()
  66
  67   def TearDown(self):
  68     """Superclass override."""
  69     super(HistoryProfileExtender, self).TearDown()
  70     for path in self._generated_temp_files:
  71       os.remove(path)
  72     self._generated_temp_files = []
  73
  74   def CleanUpAfterBatchNavigation(self):
  75     """Superclass override."""
  76     for path in self._generated_temp_files:
  77       os.remove(path)
  78     self._generated_temp_files = []
  79
  80   def _IsHistoryDBAtMaxSize(self):
  81     """Whether the history DB has reached its maximum size."""
  82     history_db_path = os.path.join(self.profile_path, "Default", "History")
  83     stat_info = os.stat(history_db_path)
  84     size = stat_info.st_size
  85
  86     max_size_threshold = 0.95
  87     bytes_in_megabyte = 2**20
  88     max_size = (bytes_in_megabyte *
  89         HistoryProfileExtender._HISTORY_DB_MAX_SIZE_IN_MB * max_size_threshold)
  90     return size > max_size