Add external function to get cgroup stats

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)

cgroups/fs/apply_raw.go

@@ -11,15 +11,15 @@ import (
 )
 
 var (
-	subsystems = []subsystem{
+	subsystems = map[string]subsystem{
-		&devicesGroup{},
+		"devices":    &devicesGroup{},
-		&memoryGroup{},
+		"memory":     &memoryGroup{},
-		&cpuGroup{},
+		"cpu":        &cpuGroup{},
-		&cpusetGroup{},
+		"cpuset":     &cpusetGroup{},
-		&cpuacctGroup{},
+		"cpuacct":    &cpuacctGroup{},
-		&blkioGroup{},
+		"blkio":      &blkioGroup{},
-		&perfEventGroup{},
+		"perf_event": &perfEventGroup{},
-		&freezerGroup{},
+		"freezer":    &freezerGroup{},
 	}
 )
 
@@ -73,6 +73,35 @@ func Apply(c *cgroups.Cgroup, pid int) (cgroups.ActiveCgroup, error) {
 	return d, nil
 }
 
+func GetStats(c *cgroups.Cgroup, subsystem string, pid int) (map[string]float64, error) {
+	cgroupRoot, err := cgroups.FindCgroupMountpoint("cpu")
+	if err != nil {
+		return nil, err
+	}
+	cgroupRoot = filepath.Dir(cgroupRoot)
+
+	if _, err := os.Stat(cgroupRoot); err != nil {
+		return nil, fmt.Errorf("cgroups fs not found")
+	}
+
+	cgroup := c.Name
+	if c.Parent != "" {
+		cgroup = filepath.Join(c.Parent, cgroup)
+	}
+
+	d := &data{
+		root:   cgroupRoot,
+		cgroup: cgroup,
+		c:      c,
+		pid:    pid,
+	}
+	sys, exists := subsystems[subsystem]
+	if !exists {
+		return nil, fmt.Errorf("subsystem %s does not exist", subsystem)
+	}
+	return sys.Stats(d)
+}
+
 func (raw *data) path(subsystem string) (string, error) {
 	initPath, err := cgroups.GetInitCgroupDir(subsystem)
 	if err != nil {

cgroups/fs/blkio.go

@@ -24,6 +24,36 @@ func (s *blkioGroup) Remove(d *data) error {
 	return removePath(d.path("blkio"))
 }
 
+/*
+examples:
+
+    blkio.sectors
+    8:0 6792
+
+    blkio.io_service_bytes
+    8:0 Read 1282048
+    8:0 Write 2195456
+    8:0 Sync 2195456
+    8:0 Async 1282048
+    8:0 Total 3477504
+    Total 3477504
+
+    blkio.io_serviced
+    8:0 Read 124
+    8:0 Write 104
+    8:0 Sync 104
+    8:0 Async 124
+    8:0 Total 228
+    Total 228
+
+    blkio.io_queued
+    8:0 Read 0
+    8:0 Write 0
+    8:0 Sync 0
+    8:0 Async 0
+    8:0 Total 0
+    Total 0
+*/
 func (s *blkioGroup) Stats(d *data) (map[string]float64, error) {
 	var (
 		paramData = make(map[string]float64)

cgroups/fs/cpuacct.go

@@ -61,7 +61,8 @@ func (s *cpuacctGroup) Stats(d *data) (map[string]float64, error) {
 	if startTime, err = s.getProcStarttime(d); err != nil {
 		return nil, err
 	}
-	paramData["percentage"] = 100.0 * ((cpuTotal/100.0)/uptime - (startTime / 100))
+	//paramData["percentage"] = 100.0 * ((cpuTotal/100.0)/uptime - (startTime / 100))
+	paramData["percentage"] = cpuTotal / (uptime - (startTime / 100))
 
 	return paramData, nil
 }