p/cpu_: add a multigraph multi-core cpu plugin

plugins/system/cpu_

@@ -0,0 +1,111 @@
+#! /bin/sh
+# Multigraph CPU plugin
+# It shows a global cpu graph, and you can drill down per-core
+
+PLUGINBASE=$(basename $0)
+
+emit_config()
+{
+cat <<'EOF'
+graph_title CPU usage
+graph_order system user nice idle iowait irq softirq
+graph_vlabel %
+graph_scale no
+graph_info This graph shows how CPU time is spent.
+graph_category system
+graph_period second
+system.label system
+system.draw AREA
+system.min 0
+system.type DERIVE
+system.info CPU time spent by the kernel in system activities
+user.label user
+user.draw STACK
+user.min 0
+user.type DERIVE
+user.info CPU time spent by normal programs and daemons
+nice.label nice
+nice.draw STACK
+nice.min 0
+nice.type DERIVE
+nice.info CPU time spent by nice(1)d programs
+idle.label idle
+idle.draw STACK
+idle.min 0
+idle.type DERIVE
+idle.info Idle CPU time
+iowait.label iowait
+iowait.draw STACK
+iowait.min 0
+iowait.type DERIVE
+iowait.info CPU time spent waiting for I/O operations to finish when there is nothing else to do.
+irq.label irq
+irq.draw STACK
+irq.min 0
+irq.type DERIVE
+irq.info CPU time spent handling interrupts
+softirq.label softirq
+softirq.draw STACK
+softirq.min 0
+softirq.type DERIVE
+softirq.info CPU time spent handling "batched" interrupts
+steal.label steal
+steal.draw STACK
+steal.min 0
+steal.type DERIVE
+steal.info The time that a virtual CPU had runnable tasks, but the virtual CPU itself was not running
+guest.label guest
+guest.draw STACK
+guest.min 0
+guest.type DERIVE
+guest.info The time spent running a virtual CPU for guest operating systems under the control of the Linux kernel.
+EOF
+}
+
+CPUS=$(grep '^cpu[0-9]' /proc/stat | cut -d ' ' -f 1)
+
+if [ "$1" = "config" ]
+then
+	echo multigraph $PLUGINBASE
+	emit_config
+	# Emit one subgraph per core
+	for cpu in $CPUS
+	do
+		echo multigraph $PLUGINBASE.$cpu
+		emit_config
+	done
+
+	exit 0
+fi
+
+emit_values()
+{
+	while read key system user nice idle iowait irq softirq steal guest unused
+	do
+		[ "$key" != "$1" ] && continue
+		cat <<EOF
+system.value $system
+user.value $user
+nice.value $nice
+idle.value $idle
+iowait.value $iowait
+irq.value $irq
+softirq.value $softirq
+steal.value $steal
+guest.value $guest
+EOF
+	done < /proc/stat
+}
+
+# Values
+echo multigraph $PLUGINBASE
+emit_values cpu
+
+# Emit one subgraph per core
+for cpu in $CPUS
+do
+	echo multigraph $PLUGINBASE.$cpu
+	emit_values $cpu
+done
+
+exit 0