diff -r 000000000000 -r 6474c204b198 tools/trace-malloc/histogram.pl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/trace-malloc/histogram.pl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,64 @@
+#!/usr/bin/perl -w
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This program produces a ``class histogram'' of the live objects, one
+# line per class, with the total number of objects allocated, and
+# total number of bytes attributed to those objects.
+
+use 5.004;
+use strict;
+use Getopt::Long;
+
+# So we can find TraceMalloc.pm
+use FindBin;
+use lib "$FindBin::Bin";
+
+use TraceMalloc;
+
+# Collect program options
+$::opt_help = 0;
+$::opt_types = "${FindBin::Bin}/types.dat";
+
+GetOptions("help", "types=s");
+
+if ($::opt_help) {
+    die "usage: histogram.pl [options] <dumpfile>
+  --help          Display this message
+  --types=<file>  Read type heuristics from <file>";
+}
+
+# Initialize type inference juju from the type file specified by
+# ``--types''.
+if ($::opt_types) {
+    TraceMalloc::init_type_inference($::opt_types);
+}
+
+# Read the dump file, collecting count and size information for each
+# object that's detected.
+
+# This'll hold a record for each class that we detect
+$::Classes = { };
+
+sub collect_objects($) {
+    my ($object) = @_;
+    my $type = $object->{'type'};
+
+    my $entry = $::Classes{$type};
+    if (! $entry) {
+        $entry = $::Classes{$type} = { '#count#' => 0, '#bytes#' => 0 };
+    }
+
+    $entry->{'#count#'} += 1;
+    $entry->{'#bytes#'} += $object->{'size'};
+}
+
+TraceMalloc::read(\&collect_objects);
+
+# Print one line per class, sorted with the classes that accumulated
+# the most bytes first.
+foreach my $class (sort { $::Classes{$b}->{'#bytes#'} <=> $::Classes{$a}->{'#bytes#'} } keys %::Classes) {
+    print "$class $::Classes{$class}->{'#count#'} $::Classes{$class}->{'#bytes#'}\n";
+}