* linux/irqstats: Make --logarithmic and enhance information

plugins/node.d.linux/irqstats.in

@@ -136,17 +136,25 @@ if (defined $ARGV[0] && $ARGV[0] eq 'config') {
     print 'graph_title Individual interrupts',
       defined($cpu) ? " on CPU $cpu\n" : "\n";
     print <<EOM;
-graph_args --base 1000 -l 0;
+graph_args --base 1000 --logarithmic
 graph_vlabel interrupts / \${graph_period}
 graph_category system
+graph_info Shows the number of different IRQs received by the kernel.  High disk or network traffic can cause a high number of interrupts (with good hardware and drivers this will be less so). Sudden high interrupt activity with no associated higher system activity is not normal.
+
 EOM
     print join(' ', 'graph_order', map {"i" . $_->{irq}} @irqs), "\n";
     for my $irq (@irqs) {
 	my $f = ($irq->{label} || $irq->{irq});
 	$f = $irq->{irq} if (length ($f) > 47);
 	print "i", $irq->{irq}, '.label ', $f, "\n";
-	print "i", $irq->{irq}, '.info Interrupt ', $irq->{irq}, ', for device(s): ', $irq->{label}, "\n"
-	  if $irq->{label};
+	if ( $irq->{label} ) {
+	  print "i", $irq->{irq}, '.info Interrupt ', $irq->{irq}, ', for device(s): ', $irq->{label}, "\n"
+	} elsif ( $irq->{irq} =~ /NMI/i ) {
+	  print "i", $irq->{irq}, ".info Nonmaskable interrupt. Either 0 or quite high. If it's normaly 0 then just one NMI will often mark some hardware failure.\n";
+	} elsif ( $irq->{irq} =~ /LOC/i ) {
+	  print "i", $irq->{irq}, ".info Local (pr. CPU core) APIC timer interrupt.  Until 2.6.21 normaly 250 or 1000 pr second. On modern 'tickless' kernels it more or less reflects how busy the machine is.\n";
+	}
+
 	print "i", $irq->{irq}, ".type DERIVE\n";
 	print "i", $irq->{irq}, ".min 0\n";
 	print_thresholds("i$irq->{irq}");