diff --git a/stackcollapse-pmc.pl b/stackcollapse-pmc.pl
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+#!/usr/bin/env perl
+#
+# Copyright (c) 2014 Ed Maste.  All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+#
+# stackcollapse-pmc.pl		collapse hwpmc samples into single lines.
+#
+# Parses a list of multiline stacks generated by "hwpmc -G", and outputs a
+# semicolon-separated stack followed by a space and a count.
+#
+# Usage:
+#   pmcstat -S unhalted-cycles -O pmc.out
+#   pmcstat -R pmc.out -z16 -G pmc.graph
+#   stackcollapse-pmc.pl pmc.graph > pmc.stack
+#
+# Example input:
+#
+# 03.07%  [17]       witness_unlock @ /boot/kernel/kernel
+#  70.59%  [12]        __mtx_unlock_flags
+#   16.67%  [2]          selfdfree
+#    100.0%  [2]           sys_poll
+#     100.0%  [2]            amd64_syscall
+#   08.33%  [1]          pmap_ts_referenced
+#    100.0%  [1]           vm_pageout
+#     100.0%  [1]            fork_exit
+# ...
+#
+# Example output:
+#
+# amd64_syscall;sys_poll;selfdfree;__mtx_unlock_flags;witness_unlock 2
+# amd64_syscall;sys_poll;pmap_ts_referenced;__mtx_unlock_flagsgeout;fork_exit 1
+# ...
+
+use warnings;
+use strict;
+
+my @stack;
+my $prev_count;
+my $prev_indent = -1;
+
+foreach (<>) {
+	if (m/^( *)[0-9.]+%  \[([0-9]+)\]\s*(\S+)/) {
+		my $indent = length($1);
+		if ($indent <= $prev_indent) {
+			print join(';', reverse(@stack[0 .. $prev_indent])) .
+			    " $prev_count\n";
+		}
+		$stack[$indent] = $3;
+		$prev_count = $2;
+		$prev_indent = $indent;
+	}
+}
+print join(';', reverse(@stack[0 .. $prev_indent])) .  " $prev_count\n";