cgroup: improve test to find cgroup compatibility issues (pingcap#41347)

close pingcap#39786

util/cgroup/cgroup_cpu.go

@@ -21,6 +21,8 @@ import (
 	"github.com/pingcap/errors"
 )
 
+var errNoCPUControllerDetected = errors.New("no cpu controller detected")
+
 // Helper function for getCgroupCPU. Root is always "/", except in tests.
 func getCgroupCPU(root string) (CPUUsage, error) {
 	path, err := detectControlPath(filepath.Join(root, procPathCGroup), "cpu,cpuacct")
@@ -30,7 +32,7 @@ func getCgroupCPU(root string) (CPUUsage, error) {
 
 	// No CPU controller detected
 	if path == "" {
-		return CPUUsage{}, errors.New("no cpu controller detected")
+		return CPUUsage{}, errNoCPUControllerDetected
 	}
 
 	mount, ver, err := getCgroupDetails(filepath.Join(root, procPathMountInfo), path, "cpu,cpuacct")

util/cgroup/cgroup_cpu_test.go

@@ -42,9 +42,13 @@ func TestGetCgroupCPU(t *testing.T) {
 		}()
 	}
 	cpu, err := GetCgroupCPU()
-	require.NoError(t, err)
-	require.NotZero(t, cpu.Period)
-	require.Less(t, int64(1), cpu.Period)
+	if err == errNoCPUControllerDetected {
+		require.False(t, InContainer(), "Please check linux version > v4.7.x. This is related to cgroup compatibility.")
+	} else {
+		require.NoError(t, err)
+		require.NotZero(t, cpu.Period)
+		require.Less(t, int64(1), cpu.Period)
+	}
 	close(exit)
 	wg.Wait()
 }