Add a test for checking objects reported by DevTools memory instrumentation not allocated by tcmall…

chrome/test/pyautolib/remote_inspector_client.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 """Chrome remote inspector utility for pyauto tests.
 
 This script provides a python interface that acts as a front-end for Chrome's
 remote inspector module, communicating via sockets to interact with Chrome in
 the same way that the Developer Tools does.  This -- in theory -- should allow
@@ skipping 693 matching lines @@
 class NativeMemorySnapshot(object):
   """Class representing native memory snapshot captured by Chromium DevTools.
 
   It is just a convenient wrapper around the snapshot structure returned over
   the remote debugging protocol. The raw snapshot structure is defined in
   WebKit/Source/WebCore/inspector/Inspector.json
 
   Public Methods:
     GetProcessPrivateMemorySize: The process total size.
     GetUnknownSize: Size of not instrumented parts.
+    GetInstrumentedObjectsCount: Number of instrumented objects traversed by
+        DevTools memory instrumentation.
+    GetNumberOfInstrumentedObjectsNotInHeap: Number of instrumented objects
+        visited by DevTools memory instrumentation that haven't been allocated
+        by tcmalloc.
     FindMemoryBlock: Given an array of memory block names return the block.
   """
   def __init__(self, root_block):
     self._root = root_block
 
   def GetProcessPrivateMemorySize(self):
     return self._root['size']
 
   def GetUnknownSize(self):
     """Size of the memory whose owner is unknown to DevTools."""
     known_size = 0
     for child in self._root['children']:
       known_size += child['size']
     return self.GetProcessPrivateMemorySize() - known_size
 
+  def GetInstrumentedObjectsCount(self):
+    """Returns number of objects visited by DevTools memory instrumentation.
+
+    Returns:
+      None if the number is not available.

[dennis_jeffrey, 2012/10/04 22:02:57]

nit: I'd prefer the "Returns:" section to fully describe what is returned by
this function, rather than only stating what is returned in the exceptional
case.  But that would basically cause you to have to repeat what's in the
one-line header of this docstring, which adds redundancy.  So while it seems
weird to me that the "Returns:" section itself only tells part of the story, I
think it's probably ok here.

[yurys, 2012/10/05 07:34:53]

Done. Changed the text to "Number of known instrumented objects or None if it is
not available."

Personally I don't like the fact that the information is repeated 4 times: 1) in
the method's name; 2) in the list of public methods; 3) in the method's 1-line
description; 4) in the return value description. The method itself is trivial
and it would be easier to skim through its code to learn details that are not
obvious from its name(like what it returns if the number is not available) than
reading all the commentaries.

+    """
+    memory_block = self.FindMemoryBlock(['ProcessPrivateMemory',
+        'InstrumentedObjectsCount'])
+    if not memory_block is None:
+      return memory_block['size']
+    return None
+
+  def GetNumberOfInstrumentedObjectsNotInHeap(self):
+    """Returns number of instrumented objects unknown to tcmalloc.
+
+    Returns:
+      None if the number is not available.
+    """
+    memory_block = self.FindMemoryBlock(['ProcessPrivateMemory',
+        'InstrumentedButNotAllocatedObjectsCount'])
+    if not memory_block is None:
+      return memory_block['size']
+    return None
+
   def FindMemoryBlock(self, path):
     """Find memory block with given path.
 
     Args:
       path: Array of block names, first element is the root block
             name, last one is the name of the block to find.
 
     Returns:
       Memory block with given path or None.
     """
@@ skipping 413 matching lines @@
 
     Returns:
       A human-readable string representation of the given number of bytes.
     """
     if num_bytes < 1024:
       return '%d B' % num_bytes
     elif num_bytes < 1048576:
       return '%.2f KB' % (num_bytes / 1024.0)
     else:
       return '%.2f MB' % (num_bytes / 1048576.0)