Added some comments and a warning message to pyauto perf tests in perf.py.

chrome/test/functional/perf.py

 #!/usr/bin/python
 # Copyright (c) 2011 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.
 
 """Basic pyauto performance tests.
 
 For tests that need to be run for multiple iterations (e.g., so that average
 and standard deviation values can be reported), the default number of iterations
 run for each of these tests is specified by |_DEFAULT_NUM_ITERATIONS|.
@@ skipping 94 matching lines @@
     if values:
       avg = float(sum(values)) / len(values)
       if len(values) > 1:
         temp_vals = [math.pow(x - avg, 2) for x in values]
         std_dev = math.sqrt(sum(temp_vals) / (len(temp_vals) - 1))
     return avg, std_dev
 
   def _OutputPerfGraphValue(self, description, value):
     """Outputs a performance value to have it graphed on the performance bots.
 
-    Only used for ChromeOS.
+    Only used for ChromeOS.  The performance bots have a 30-character limit on
+    the length of the description for a performance value.  Any characters
+    beyond that are truncated before results are stored in the autotest
+    database.
 
     Args:
-      description: A string description of the performance value.
+      description: A string description of the performance value.  This will
+                   be truncated to 30 characters when stored in the autotest
+                   database.
       value: A numeric value representing a single performance measurement.
     """
     if self.IsChromeOS():
+      if len(description) > 30:
+        logging.warning('The description "%s" will be truncated to "%s" '
+                        '(length 30) when added to the autotest database.',
+                        description, description[:30])
       print '\n%s(\'%s\', %.2f)%s' % (self._PERF_OUTPUT_MARKER_PRE, description,
                                       value, self._PERF_OUTPUT_MARKER_POST)
 
   def _PrintSummaryResults(self, description, values, units):
     """Logs summary measurement information.
 
+    This function computes and outputs the average and standard deviation of
+    the specified list of value measurements.  It also invokes
+    _OutputPerfGraphValue() with the computed *average* value, to ensure the
+    average value can be plotted in a performance graph.
+
     Args:
       description: A string description for the specified results.
       values: A list of numeric value measurements.
       units: A string specifying the units for the specified measurements.
     """
     logging.info('Results for: ' + description)
     if values:
       avg, std_dev = self._AvgAndStdDev(values)
       logging.info('Number of iterations: %d', len(values))
       for val in values:
@@ skipping 450 matching lines @@
     # Wait until the final result is computed, then retrieve and output it.
     # TODO(dennisjeffrey): Have all tests in this class use JSON.stringify()
     # to send results back from the Javascript.
     js = 'window.domAutomationController.send("" + final_average_fps);'
     self.assertTrue(
         self.WaitUntil(
             lambda: self.ExecuteJavascript(js, tab_index=1) != '-1',
             timeout=300, expect_retval=True, retry_sleep=0.25),
         msg='Timed out when waiting for test result.')
     result = float(self.ExecuteJavascript(js, tab_index=1))
-    logging.info('Result for %s: %.2f FPS (average)' % (description, result))
+    logging.info('Result for %s: %.2f FPS (average)', description, result)
     self._OutputPerfGraphValue('%s_%s' % ('FPS', description), result)
 
   def testFlashGaming(self):
     """Runs a simple flash gaming benchmark test."""
     webpage_url = self.GetHttpURLForDataPath('pyauto_private', 'flash',
                                              'FlashGamingTest2.html')
     self._RunFlashTestForAverageFPS(webpage_url, 'FlashGaming')
 
   def testFlashText(self):
     """Runs a simple flash text benchmark test."""
@@ skipping 27 matching lines @@
         json_result += "}";
         window.domAutomationController.send(json_result);
     """
     result = eval(self.ExecuteJavascript(js_result, tab_index=1))
     for benchmark in result:
       mflops = result[benchmark][0]
       mem = result[benchmark][1]
       if benchmark.endswith('_mflops'):
         benchmark = benchmark[:benchmark.find('_mflops')]
       logging.info('Results for ScimarkGui_' + benchmark + ':')
-      logging.info('  %.2f MFLOPS' % mflops)
-      logging.info('  %.2f MB' % mem)
+      logging.info('  %.2f MFLOPS', mflops)
+      logging.info('  %.2f MB', mem)
       self._OutputPerfGraphValue(
           '%s_ScimarkGui-%s-MFLOPS' % ('MFLOPS', benchmark), mflops)
       self._OutputPerfGraphValue(
           '%s_ScimarkGui-%s-Mem' % ('MB', benchmark), mem)
 
 
 class PerfTestServerRequestHandler(SimpleHTTPServer.SimpleHTTPRequestHandler):
   """Request handler for the local performance test server."""
 
   def _IgnoreHandler(self, unused_args):
@@ skipping 13 matching lines @@
       args: A dictionary of arguments for the current GET request.  Must
             contain 'filename' and 'mb' keys that refer to the name of the
             file to create and its desired size, respectively.
     """
     megabytes = None
     filename = None
     try:
       megabytes = int(args['mb'][0])
       filename = args['filename'][0]
     except (ValueError, KeyError, IndexError), e:
-      logging.exception('Server error creating file: %s' % e)
+      logging.exception('Server error creating file: %s', e)
     assert megabytes and filename
     with open(os.path.join(self.server.docroot, filename), 'wb') as f:
       f.write('X' * 1024 * 1024 * megabytes)
     self.send_response(200)
     self.end_headers()
 
   def _DeleteFileHandler(self, args):
     """A GET handler that deletes the specified local file.
 
     Args:
       args: A dictionary of arguments for the current GET request.  Must
             contain a 'filename' key that refers to the name of the file
             to delete, relative to the server's document root.
     """
     filename = None
     try:
       filename = args['filename'][0]
     except (KeyError, IndexError), e:
-      logging.exception('Server error deleting file: %s' % e)
+      logging.exception('Server error deleting file: %s', e)
     assert filename
     try:
       os.remove(os.path.join(self.server.docroot, filename))
     except OSError, e:
-      logging.warning('OS error removing file: %s' % e)
+      logging.warning('OS error removing file: %s', e)
     self.send_response(200)
     self.end_headers()
 
   def _StartUploadHandler(self, args):
     """A GET handler to serve a page that uploads the given amount of data.
 
     When the page loads, the specified amount of data is automatically
     uploaded to the same local server that is handling the current request.
 
     Args:
       args: A dictionary of arguments for the current GET request.  Must
             contain an 'mb' key that refers to the size of the data to
             upload.
     """
     megabytes = None
     try:
       megabytes = int(args['mb'][0])
     except (ValueError, KeyError, IndexError), e:
-      logging.exception('Server error starting upload: %s' % e)
+      logging.exception('Server error starting upload: %s', e)
     assert megabytes
     script = """
         <html>
           <head>
             <script type='text/javascript'>
               function startUpload() {
                 var megabytes = %s;
                 var data = Array((1024 * 1024 * megabytes) + 1).join('X');
                 var boundary = '***BOUNDARY***';
                 var xhr = new XMLHttpRequest();
@@ skipping 142 matching lines @@
     """Identifies the port number to which the server is currently bound.
 
     Returns:
       The numeric port number to which the server is currently bound.
     """
     return self._server.server_address[1]
 
 
 if __name__ == '__main__':
   pyauto_functional.Main()