#!/usr/bin/perl -w

=pod

=encoding UTF-8

=head1 NAME

buddyinfo - Plugin to monitor memory fragmentation on Linux systems.

=head1 APPLICABLE SYSTEMS

Linux 2.5.40+, 2.6.x

=head1 CONFIGURATION

None needed.

To optionally use a logarithmic scale on the graphs, define the
environment variable logarithmic. For example:

 [buddyinfo]
 env.logarithmic yes

=head1 INTERPRETATION

Linux manages virtual memory on a page granularity. There are some operations
however that require physically contiguous pages to be allocated by the kernel.
Such allocations may fail if the memory gets fragmented and even though there
are enough pages free, but they are not contiguous.

This plugin monitors the amount of contiguous areas, called higher order pages.
The order means the exponent of two of the size of the area, so order 2 means
2^2 = 4 pages.

=head1 SEE ALSO

See C<Documentation/filesystems/proc.txt> in the Linux source tree for the
description of the buddyinfo file.

=head1 MAGIC MARKERS

 #%# family=manual
 #%# capabilities=autoconf

=head1 AUTHOR

Gábor Gombás <gombasg@sztaki.hu>

=head1 LICENSE

GPLv2 or later

=cut

use strict;
use Munin::Plugin;
use POSIX;
use Carp;

need_multigraph();

if ($ARGV[0] and $ARGV[0] eq 'autoconf') {
	if (-f "/proc/buddyinfo") {
		print "yes\n";
	}
	else {
		print "no (/proc/buddyinfo is missing)\n";
	}
	exit 0;
}

# The most common page size is 4k, but it is not universal
my $pagesize = POSIX::sysconf(&POSIX::_SC_PAGESIZE) / 1024;

my $zones = {};

open(FH, '< /proc/buddyinfo')
	or croak "Failed to open '/proc/buddyinfo': $!";
while (my $line = <FH>) {
	chomp $line;

	$line =~ m/Node (\d+), zone\s+(\S+)\s+(\S.*)$/;
	my $name = "Node $1, zone $2";
	my @cnt = split(/ +/, $3);
	$zones->{$name} = \@cnt;
}
close FH;

my $totals = [];
foreach my $zone (keys %$zones) {
	for my $i (0 .. $#{$zones->{$zone}}) {
		$totals->[$i] += $zones->{$zone}->[$i]
	}
}

sub do_config {
	print "multigraph buddyinfo\n";
	print "graph_title Memory fragmentation\n";
	print "graph_args --base 1024";
	if (exists $ENV{"logarithmic"}) {
		print " --logarithmic --units=si\n";
	} else {
		print " --lower-limit 0\n";
	}
	print "graph_vlabel pages free\n";
	print "graph_category system\n";
	print "graph_info This graph shows the number of free pages of different size\n";
	print "graph_order " . join(' ', map { "order$_" } (0 .. $#{$totals})) . "\n";
	for my $i (0 .. $#{$totals}) {
		print "order$i.label Order $i\n";
		print "order$i.info Number of order $i (" . ($pagesize * 2 ** $i) . " KiB) pages\n";
		print "order$i.type GAUGE\n";
		print "order$i.min 0\n";
	}
	for my $zone (sort keys %$zones) {
		my $zoneid = $zone;
		$zoneid = clean_fieldname($zone);

		print "multigraph buddyinfo.$zoneid\n";
		print "graph_title Memory fragmentation in $zone\n";
		print "graph_args --base 1024";
		if (exists $ENV{"logarithmic"}) {
			print " --logarithmic --units=si\n";
		} else {
			print " --lower-limit 0\n";
		}
		print "graph_vlabel pages free\n";
		print "graph_category system\n";
		print "graph_info This graph shows the number of free pages in $zone\n";
		print "graph_order " .
			join(' ', map { "order$_" } (0 .. $#{$zones->{$zone}})) . "\n";
		for my $i (0 .. $#{$zones->{$zone}}) {
			print "order$i.label Order $i\n";
			print "order$i.info Number of order $i (" .
				($pagesize * 2 ** $i) . " KiB) pages\n";
			print "order$i.type GAUGE\n";
			print "order$i.min 0\n";
		}
	}
}

sub do_fetch {
	print "multigraph buddyinfo\n";
	for my $i (0 .. $#{$totals}) {
		print "order$i.value " . $totals->[$i] . "\n";
	}
	for my $zone (sort keys %$zones) {
		my $zoneid = $zone;
		$zoneid =~ tr/ ,/__/;

		print "multigraph buddyinfo.$zoneid\n";
		for my $i (0 .. $#{$zones->{$zone}}) {
			print "order$i.value " . $zones->{$zone}->[$i] . "\n";
		}
	}
}

if ($ARGV[0] and $ARGV[0] eq 'config') {
	do_config();
	exit 0;
}

do_fetch();