add cpucalc, updatecpu method

container.go

@@ -24,11 +24,26 @@ func NewWidgets(id string) *Widgets {
 	return &Widgets{cid, mkGauge(), mkGauge()}
 }
 
+type CpuCalc struct {
+	lastCpu    uint64
+	lastSysCpu uint64
+}
+
+func (c *CpuCalc) Utilization(cpu uint64, syscpu uint64, ncpus int) int {
+	cpudiff := float64(cpu) - float64(c.lastCpu)
+	syscpudiff := float64(syscpu) - float64(c.lastSysCpu)
+	util := round((cpudiff / syscpudiff * 100) * float64(ncpus))
+	c.lastCpu = cpu
+	c.lastSysCpu = syscpu
+	return util
+}
+
 type Container struct {
 	id      string
 	widgets *Widgets
 	stats   chan *docker.Stats
 	done    chan bool
+	cpucalc *CpuCalc
 }
 
 func NewContainer(cid string) *Container {
@@ -37,6 +52,7 @@ func NewContainer(cid string) *Container {
 		widgets: NewWidgets(cid),
 		stats:   make(chan *docker.Stats),
 		done:    make(chan bool),
+		cpucalc: &CpuCalc{},
 	}
 }
 
@@ -57,14 +73,20 @@ func (c *Container) Collect(client *docker.Client) {
 	go func() {
 		for s := range c.stats {
 			c.UpdateMem(s.MemoryStats.Usage, s.MemoryStats.Limit)
+			c.UpdateCPU(s.CPUStats.CPUUsage.TotalUsage, s.CPUStats.SystemCPUUsage, len(s.CPUStats.CPUUsage.PercpuUsage))
 		}
 	}()
 
 }
 
-func (c *Container) UpdateCPU(total uint64, system uint64) {
-	c.widgets.cpu.BarColor = colorScale(n)
-	c.widgets.cpu.Percent = n
+func (c *Container) UpdateCPU(total uint64, system uint64, ncpus int) {
+	util := c.cpucalc.Utilization(total, system, ncpus)
+	c.widgets.cpu.Label = fmt.Sprintf("%s%%", strconv.Itoa(util))
+	c.widgets.cpu.BarColor = colorScale(util)
+	if util < 5 && util > 0 {
+		util = 5
+	}
+	c.widgets.cpu.Percent = util
 }
 
 func (c *Container) UpdateMem(cur uint64, limit uint64) {