libcontainer/intelrdt: rm init() from intelrdt.go

Use sync.Once to init Intel RDT when needed for a small speedup to
operations which do not require Intel RDT.

Simplify IntelRdtManager initialization in LinuxFactory.

Signed-off-by: Xiaochen Shen <xiaochen.shen@intel.com>

libcontainer/factory_linux.go

@@ -148,9 +148,13 @@ func RootlessCgroupfs(l *LinuxFactory) error {
 // containers that use the Intel RDT "resource control" filesystem to
 // create and manage Intel RDT resources (e.g., L3 cache, memory bandwidth).
 func IntelRdtFs(l *LinuxFactory) error {
+	if !intelrdt.IsCATEnabled() && !intelrdt.IsMBAEnabled() {
+		l.NewIntelRdtManager = nil
+	} else {
 		l.NewIntelRdtManager = func(config *configs.Config, id string, path string) intelrdt.Manager {
 			return intelrdt.NewManager(config, id, path)
 		}
+	}
 	return nil
 }
 
@@ -272,7 +276,7 @@ func (l *LinuxFactory) Create(id string, config *configs.Config) (Container, err
 		newgidmapPath: l.NewgidmapPath,
 		cgroupManager: l.NewCgroupsManager(config.Cgroups, nil),
 	}
-	if intelrdt.IsCATEnabled() || intelrdt.IsMBAEnabled() {
+	if l.NewIntelRdtManager != nil {
 		c.intelRdtManager = l.NewIntelRdtManager(config, id, "")
 	}
 	c.state = &stoppedState{c: c}
@@ -314,13 +318,13 @@ func (l *LinuxFactory) Load(id string) (Container, error) {
 		root:                 containerRoot,
 		created:              state.Created,
 	}
+	if l.NewIntelRdtManager != nil {
+		c.intelRdtManager = l.NewIntelRdtManager(&state.Config, id, state.IntelRdtPath)
+	}
 	c.state = &loadedState{c: c}
 	if err := c.refreshState(); err != nil {
 		return nil, err
 	}
-	if intelrdt.IsCATEnabled() || intelrdt.IsMBAEnabled() {
-		c.intelRdtManager = l.NewIntelRdtManager(&state.Config, id, state.IntelRdtPath)
-	}
 	return c, nil
 }
 

libcontainer/intelrdt/cmt.go

@@ -6,6 +6,7 @@ var (
 
 // Check if Intel RDT/CMT is enabled.
 func IsCMTEnabled() bool {
+	featuresInit()
 	return cmtEnabled
 }
 

libcontainer/intelrdt/intelrdt.go

@@ -195,6 +195,9 @@ var (
 	mbaEnabled bool
 	// The flag to indicate if Intel RDT/MBA Software Controller is enabled
 	mbaScEnabled bool
+
+	// For Intel RDT initialization
+	initOnce sync.Once
 )
 
 type intelRdtData struct {
@@ -203,8 +206,9 @@ type intelRdtData struct {
 	pid    int
 }
 
-// Check if Intel RDT sub-features are enabled in init()
-func init() {
+// Check if Intel RDT sub-features are enabled in featuresInit()
+func featuresInit() {
+	initOnce.Do(func() {
 		// 1. Check if hardware and kernel support Intel RDT sub-features
 		flagsSet, err := parseCpuInfoFile("/proc/cpuinfo")
 		if err != nil {
@@ -236,7 +240,6 @@ func init() {
 				mbaEnabled = true
 			}
 		}
-
 		if flagsSet.MBMTotal || flagsSet.MBMLocal || flagsSet.CMT {
 			if _, err := os.Stat(filepath.Join(intelRdtRoot, "info", "L3_MON")); err != nil {
 				return
@@ -252,6 +255,7 @@ func init() {
 				cmtEnabled = true
 			}
 		}
+	})
 }
 
 // Return the mount point path of Intel RDT "resource control" filesysem
@@ -525,16 +529,19 @@ func WriteIntelRdtTasks(dir string, pid int) error {
 
 // Check if Intel RDT/CAT is enabled
 func IsCATEnabled() bool {
+	featuresInit()
 	return catEnabled
 }
 
 // Check if Intel RDT/MBA is enabled
 func IsMBAEnabled() bool {
+	featuresInit()
 	return mbaEnabled
 }
 
 // Check if Intel RDT/MBA Software Controller is enabled
 func IsMBAScEnabled() bool {
+	featuresInit()
 	return mbaScEnabled
 }
 

libcontainer/intelrdt/mbm.go

@@ -9,6 +9,7 @@ var (
 
 // Check if Intel RDT/MBM is enabled.
 func IsMBMEnabled() bool {
+	featuresInit()
 	return mbmEnabled
 }
 

utils_linux.go

@@ -13,7 +13,6 @@ import (
 	"github.com/opencontainers/runc/libcontainer"
 	"github.com/opencontainers/runc/libcontainer/cgroups/systemd"
 	"github.com/opencontainers/runc/libcontainer/configs"
-	"github.com/opencontainers/runc/libcontainer/intelrdt"
 	"github.com/opencontainers/runc/libcontainer/specconv"
 	"github.com/opencontainers/runc/libcontainer/utils"
 	"github.com/opencontainers/runtime-spec/specs-go"
@@ -57,9 +56,6 @@ func loadFactory(context *cli.Context) (libcontainer.Factory, error) {
 	}
 
 	intelRdtManager := libcontainer.IntelRdtFs
-	if !intelrdt.IsCATEnabled() && !intelrdt.IsMBAEnabled() {
-		intelRdtManager = nil
-	}
 
 	// We resolve the paths for {newuidmap,newgidmap} from the context of runc,
 	// to avoid doing a path lookup in the nsexec context. TODO: The binary