Heap profiling: add logging of heap memory stats (capacity, used) under 'log-gc' flag.

tools/process-heap-prof.py

 #!/usr/bin/env python
 #
 # Copyright 2009 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 21 matching lines @@
 # to produce heap usage histograms.
 
 # Sample usage:
 # $ ./shell --log-gc script.js
 # $ tools/process-heap-prof.py v8.log | hp2ps -c > script-heap-graph.ps
 # ('-c' enables color, see hp2ps manual page for more options)
 
 import csv, sys, time
 
 def process_logfile(filename):
+  first_call_time = None
   sample_time = 0.0
   sampling = False
   try:
     logfile = open(filename, 'rb')
     try:
       logreader = csv.reader(logfile)
 
       print('JOB "v8"')
       print('DATE "%s"' % time.asctime(time.localtime()))
       print('SAMPLE_UNIT "seconds"')
       print('VALUE_UNIT "bytes"')
 
       for row in logreader:
         if row[0] == 'heap-sample-begin' and row[1] == 'Heap':
-          sample_time = float(row[3]) + float(row[4])/1000000.0
+          sample_time = float(row[3])/1000.0
+          if first_call_time == None:
+            first_call_time = sample_time
+          sample_time -= first_call_time
           print('BEGIN_SAMPLE %.2f' % sample_time)
           sampling = True
         elif row[0] == 'heap-sample-end' and row[1] == 'Heap':
           print('END_SAMPLE %.2f' % sample_time)
           sampling = False
         elif row[0] == 'heap-sample-item' and sampling:
           print('%s %d' % (row[1], int(row[3])))
     finally:
       logfile.close()
   except:
     sys.exit('can\'t open %s' % filename)
 
 process_logfile(sys.argv[1])