diff --git a/tools/historic_memory_usage.py b/tools/historic_memory_usage.py
index 376426f..bb08a2e 100755
--- a/tools/historic_memory_usage.py
+++ b/tools/historic_memory_usage.py
@@ -10,13 +10,13 @@
 # It will then run the oldest and newest such commit, and gradually fill in
 # the commits in between.
 
+import historic_run
 import optparse
 import os
 import subprocess
 import sys
 import utils
 
-MASTER_COMMITS = 'gs://r8-releases/raw/master'
 APPS = ['gmscore', 'nest', 'youtube', 'gmail', 'chrome']
 COMPILERS = ['d8', 'r8']
 
@@ -31,7 +31,7 @@
                     default='gmail',
                     choices=APPS)
   result.add_option('--top',
-                    default=utils.get_HEAD_sha1(),
+                    default=historic_run.top_or_default(),
                     help='The most recent commit to test')
   result.add_option('--bottom',
                     help='The oldest commit to test')
@@ -44,84 +44,8 @@
                     help='Set timeout instead of waiting for OOM.')
   return result.parse_args(argv)
 
-
-class GitCommit(object):
-  def __init__(self, git_hash, destination_dir, destination, timestamp):
-    self.git_hash = git_hash
-    self.destination_dir = destination_dir
-    self.destination = destination
-    self.timestamp = timestamp
-
-  def __str__(self):
-    return '%s : %s (%s)' % (self.git_hash, self.destination, self.timestamp)
-
-  def __repr__(self):
-    return self.__str__()
-
-def git_commit_from_hash(hash):
-  commit_timestamp = subprocess.check_output(['git', 'show', '--no-patch',
-                                         '--no-notes', '--pretty=\'%ct\'',
-                                         hash]).strip().strip('\'')
-  destination_dir = '%s/%s/' % (MASTER_COMMITS, hash)
-  destination = '%s%s' % (destination_dir, 'r8.jar')
-  commit = GitCommit(hash, destination_dir, destination, commit_timestamp)
-  return commit
-
-def enumerate_git_commits(options):
-  top = options.top if options.top else utils.get_HEAD_sha1()
-  # TODO(ricow): if not set, search back 1000
-  if not options.bottom:
-    raise Exception('No bottom specified')
-  bottom = options.bottom
-  output = subprocess.check_output(['git', 'rev-list', '--first-parent', top])
-  found_bottom = False
-  commits = []
-  for c in output.splitlines():
-    commits.append(git_commit_from_hash(c.strip()))
-    if c.strip() == bottom:
-      found_bottom = True
-      break
-  if not found_bottom:
-    raise Exception('Bottom not found, did you not use a merge commit')
-  return commits
-
-def get_available_commits(commits):
-  cloud_commits = subprocess.check_output(['gsutil.py', 'ls', MASTER_COMMITS]).splitlines()
-  available_commits = []
-  for commit in commits:
-    if commit.destination_dir in cloud_commits:
-      available_commits.append(commit)
-  return available_commits
-
-def print_commits(commits):
-  for commit in commits:
-    print(commit)
-
-def permutate_range(start, end):
-  diff = end - start
-  assert diff >= 0
-  if diff == 1:
-    return [start, end]
-  if diff == 0:
-    return [start]
-  half = end - (diff / 2)
-  numbers = [half]
-  first_half = permutate_range(start, half - 1)
-  second_half = permutate_range(half + 1, end)
-  for index in range(len(first_half)):
-    numbers.append(first_half[index])
-    if index < len(second_half):
-      numbers.append(second_half[index])
-  return numbers
-
-def permutate(number_of_commits):
-  assert number_of_commits > 0
-  numbers = permutate_range(0, number_of_commits - 1)
-  assert all(n in numbers for n in range(number_of_commits))
-  return numbers
-
-def pull_r8_from_cloud(commit):
-  utils.download_file_from_cloud_storage(commit.destination, utils.R8_JAR)
+def make_run_on_app_command(options):
+  return lambda commit: run_on_app(options, commit)
 
 def run_on_app(options, commit):
   app = options.app
@@ -142,30 +66,14 @@
     f.write(stdout)
   print('Wrote stdout to: %s' % stdout_path)
 
-
-def benchmark(commits, options):
-  commit_permutations = permutate(len(commits))
-  count = 0
-  for index in commit_permutations:
-    count += 1
-    print('Running commit %s out of %s' % (count, len(commits)))
-    commit = commits[index]
-    if not utils.cloud_storage_exists(commit.destination):
-      # We may have a directory, but no r8.jar
-      continue
-    pull_r8_from_cloud(commit)
-    print('Running for commit: %s' % commit.git_hash)
-    run_on_app(options, commit)
-
 def main(argv):
   (options, args) = ParseOptions(argv)
   if not options.app:
      raise Exception('Please specify an app')
-  commits = enumerate_git_commits(options)
-  available_commits = get_available_commits(commits)
-  print('Running for:')
-  print_commits(available_commits)
-  benchmark(available_commits, options)
+  top = historic_run.top_or_default(options.top)
+  bottom = historic_run.bottom_or_default(options.bottom)
+  command = make_run_on_app_command(options)
+  historic_run.run(command, top, bottom)
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))
diff --git a/tools/historic_run.py b/tools/historic_run.py
new file mode 100755
index 0000000..b0f181f
--- /dev/null
+++ b/tools/historic_run.py
@@ -0,0 +1,187 @@
+#!/usr/bin/env python
+# Copyright (c) 2019, the R8 project authors. Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+# Convenience script for running a command over builds back in time. This
+# utilizes the prebuilt full r8 jars on cloud storage.  The script find all
+# commits that exists on cloud storage in the given range.  It will then run the
+# oldest and newest such commit, and gradually fill in the commits in between.
+
+import optparse
+import os
+import subprocess
+import sys
+import time
+import utils
+
+MASTER_COMMITS = 'gs://r8-releases/raw/master'
+
+def ParseOptions(argv):
+  result = optparse.OptionParser()
+  result.add_option(
+    '--cmd',
+    help='Command to run')
+  result.add_option(
+    '--top',
+    default=top_or_default(),
+    help='The most recent commit to test')
+  result.add_option(
+    '--bottom',
+    help='The oldest commit to test')
+  result.add_option(
+    '--dry-run',
+    help='Do not download or run the command, but print the actions',
+    default=False,
+    action='store_true')
+  result.add_option(
+    '--output',
+    default='build',
+    help='Directory where to output results')
+  return result.parse_args(argv)
+
+
+class GitCommit(object):
+  def __init__(self, git_hash, destination_dir, destination, timestamp):
+    self.git_hash = git_hash
+    self.destination_dir = destination_dir
+    self.destination = destination
+    self.timestamp = timestamp
+
+  def __str__(self):
+    return '%s : %s (%s)' % (self.git_hash, self.destination, self.timestamp)
+
+  def __repr__(self):
+    return self.__str__()
+
+def git_commit_from_hash(hash):
+  commit_timestamp = subprocess.check_output(['git', 'show', '--no-patch',
+                                         '--no-notes', '--pretty=\'%ct\'',
+                                         hash]).strip().strip('\'')
+  destination_dir = '%s/%s/' % (MASTER_COMMITS, hash)
+  destination = '%s%s' % (destination_dir, 'r8.jar')
+  commit = GitCommit(hash, destination_dir, destination, commit_timestamp)
+  return commit
+
+def enumerate_git_commits(top, bottom):
+  output = subprocess.check_output(['git', 'rev-list', '--first-parent', top])
+  found_bottom = False
+  commits = []
+  for c in output.splitlines():
+    commit_hash = c.strip()
+    commits.append(git_commit_from_hash(commit_hash))
+    if commit_hash == bottom:
+      found_bottom = True
+      break
+  if not found_bottom:
+    raise Exception('Bottom not found, did you not use a merge commit')
+  return commits
+
+def get_available_commits(commits):
+  cloud_commits = subprocess.check_output(
+    ['gsutil.py', 'ls', MASTER_COMMITS]).splitlines()
+  available_commits = []
+  for commit in commits:
+    if commit.destination_dir in cloud_commits:
+      available_commits.append(commit)
+  return available_commits
+
+def print_commits(commits):
+  for commit in commits:
+    print(commit)
+
+def permutate_range(start, end):
+  diff = end - start
+  assert diff >= 0
+  if diff == 1:
+    return [start, end]
+  if diff == 0:
+    return [start]
+  half = end - (diff / 2)
+  numbers = [half]
+  first_half = permutate_range(start, half - 1)
+  second_half = permutate_range(half + 1, end)
+  for index in range(len(first_half)):
+    numbers.append(first_half[index])
+    if index < len(second_half):
+      numbers.append(second_half[index])
+  return numbers
+
+def permutate(number_of_commits):
+  assert number_of_commits > 0
+  numbers = permutate_range(0, number_of_commits - 1)
+  assert all(n in numbers for n in range(number_of_commits))
+  return numbers
+
+def pull_r8_from_cloud(commit):
+  utils.download_file_from_cloud_storage(commit.destination, utils.R8_JAR)
+
+def benchmark(commits, command, dryrun=False):
+  commit_permutations = permutate(len(commits))
+  count = 0
+  for index in commit_permutations:
+    count += 1
+    print('Running commit %s out of %s' % (count, len(commits)))
+    commit = commits[index]
+    if not utils.cloud_storage_exists(commit.destination):
+      # We may have a directory, but no r8.jar
+      continue
+    if not dryrun:
+      pull_r8_from_cloud(commit)
+    print('Running for commit: %s' % commit.git_hash)
+    command(commit)
+
+def top_or_default(top=None):
+  return top if top else utils.get_HEAD_sha1()
+
+def bottom_or_default(bottom=None):
+  # TODO(ricow): if not set, search back 1000
+  if not bottom:
+    raise Exception('No bottom specified')
+  return bottom
+
+def run(command, top, bottom, dryrun=False):
+  commits = enumerate_git_commits(top, bottom)
+  available_commits = get_available_commits(commits)
+  print('Running for:')
+  print_commits(available_commits)
+  benchmark(available_commits, command, dryrun=dryrun)
+
+def make_cmd(options):
+  return lambda commit: run_cmd(options, commit)
+
+def run_cmd(options, commit):
+  cmd = [options.cmd, commit.git_hash]
+  output_path = options.output or 'build'
+  time_commit = '%s_%s' % (commit.timestamp, commit.git_hash)
+  time_commit_path = os.path.join(output_path, time_commit)
+  print ' '.join(cmd)
+  if not options.dry_run:
+    if not os.path.exists(time_commit_path):
+      os.makedirs(time_commit_path)
+    stdout_path = os.path.join(time_commit_path, 'stdout')
+    stderr_path = os.path.join(time_commit_path, 'stderr')
+    with open(stdout_path, 'w') as stdout:
+      with open(stderr_path, 'w') as stderr:
+        process = subprocess.Popen(cmd, stdout=stdout, stderr=stderr)
+        timeout = 1000
+        while process.poll() is None and timeout > 0:
+          time.sleep(1)
+          timeout -= 1
+        if process.poll() is None:
+          process.kill()
+          print "Task timed out"
+          stderr.write("timeout\n")
+  print('Wrote outputs to: %s' % time_commit_path)
+
+def main(argv):
+  (options, args) = ParseOptions(argv)
+  if not options.cmd:
+     raise Exception('Please specify a command')
+  top = top_or_default(options.top)
+  bottom = bottom_or_default(options.bottom)
+  command = make_cmd(options)
+  run(command, top, bottom, dryrun=options.dry_run)
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv[1:]))