[tools] Add script to analyze GC tracing output

BUG=

Review URL: https://codereview.chromium.org/1348763006

Cr-Commit-Position: refs/heads/master@{#30865}

tools/eval_gc_nvp.py

+#!/usr/bin/env python
+#
+# Copyright 2015 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""This script is used to analyze GCTracer's NVP output."""
+
+from argparse import ArgumentParser
+from gc_nvp_common import split_nvp
+from sys import stdin
+
+class Histogram:
+  def __init__(self, values, granularity):
+    self.values = list(values)  # copy over values
+    self.granularity = granularity
+
+  def __str__(self):
+    ret = []
+    values = list(self.values)  # copy over values
+    min_value = 0
+    while len(values) > 0:
+      max_value = min_value +  self.granularity
+      sub = [x for x in self.values if x >= min_value and x < max_value]
+      ret.append("  [{0},{1}[: {2}".format(
+        str(min_value), str(max_value),len(sub)))
+      min_value += self.granularity
+      values = [x for x in values if x not in sub]
+    return "\n".join(ret)
+
+
+class Category:
+  def __init__(self, key, histogram, granularity):
+    self.key = key
+    self.values = []
+    self.histogram = histogram
+    self.granularity = granularity
+
+  def process_entry(self, entry):
+    if self.key in entry:
+      self.values.append(float(entry[self.key]))
+
+  def __str__(self):
+    ret = [self.key]
+    ret.append("  len: {0}".format(len(self.values)))
+    if len(self.values) > 0:
+      ret.append("  min: {0}".format(min(self.values)))
+      ret.append("  max: {0}".format(max(self.values)))
+      ret.append("  avg: {0}".format(sum(self.values) / len(self.values)))
+      if self.histogram:
+        ret.append(str(Histogram(self.values, self.granularity)))
+    return "\n".join(ret)
+
+
+def main():
+  parser = ArgumentParser(description="Process GCTracer's NVP output")
+  parser.add_argument('keys', metavar='KEY', type=str, nargs='+',
+                      help='the keys (names) to process')
+  parser.add_argument('--histogram-granularity', metavar='GRANULARITY',
+                      type=int, nargs='?', default=5,
+                      help='histogram granularity (default: 5)')
+  feature_parser = parser.add_mutually_exclusive_group(required=False)
+  feature_parser.add_argument('--histogram', dest='histogram',
+                              action='store_true',
+                              help='print histogram')
+  feature_parser.add_argument('--no-histogram', dest='histogram',
+                              action='store_false',
+                              help='do not print histogram')
+  parser.set_defaults(histogram=True)
+  args = parser.parse_args()
+
+  categories = [ Category(key, args.histogram, args.histogram_granularity)
+                 for key in args.keys ]
+
+  while True:
+    line = stdin.readline()
+    if not line:
+      break
+    obj = split_nvp(line)
+    for category in categories:
+      category.process_entry(obj)
+
+  for category in categories:
+    print(category)
+
+
+if __name__ == '__main__':
+  main()