intelrdt: always init IntelRdtManager if Intel RDT is enabled

In current implementation:
Either Intel RDT is not enabled by hardware and kernel, or intelRdt is
not specified in original config, we don't init IntelRdtManager in the
container to handle intelrdt constraint. It is a tradeoff that Intel RDT
has hardware limitation to support only limited number of groups.

This patch makes a minor change to support update command:
Whether or not intelRdt is specified in config, we always init
IntelRdtManager in the container if Intel RDT is enabled. If intelRdt is
not specified in original config, we just don't Apply() to create
intelrdt group or attach tasks for this container.

In update command, we could re-enable through IntelRdtManager.Apply()
and then update intelrdt constraint.

Signed-off-by: Xiaochen Shen <[email protected]>

Author: xiaochenshen

libcontainer/factory_linux.go

@@ -213,8 +213,7 @@ func (l *LinuxFactory) Create(id string, config *configs.Config) (Container, err
 		newgidmapPath: l.NewgidmapPath,
 		cgroupManager: l.NewCgroupsManager(config.Cgroups, nil),
 	}
-	c.intelRdtManager = nil
-	if intelrdt.IsEnabled() && c.config.IntelRdt != nil {
+	if intelrdt.IsEnabled() {
 		c.intelRdtManager = l.NewIntelRdtManager(config, id, "")
 	}
 	c.state = &stoppedState{c: c}
@@ -256,8 +255,7 @@ func (l *LinuxFactory) Load(id string) (Container, error) {
 	if err := c.refreshState(); err != nil {
 		return nil, err
 	}
-	c.intelRdtManager = nil
-	if intelrdt.IsEnabled() && c.config.IntelRdt != nil {
+	if intelrdt.IsEnabled() {
 		c.intelRdtManager = l.NewIntelRdtManager(&state.Config, id, state.IntelRdtPath)
 	}
 	return c, nil

libcontainer/intelrdt/intelrdt.go

@@ -401,6 +401,10 @@ func GetIntelRdtPath(id string) (string, error) {
 
 // Applies Intel RDT configuration to the process with the specified pid
 func (m *IntelRdtManager) Apply(pid int) (err error) {
+	// If intelRdt is not specified in config, we do nothing
+	if m.Config.IntelRdt == nil {
+		return nil
+	}
 	d, err := getIntelRdtData(m.Config, pid)
 	if err != nil && !IsNotFound(err) {
 		return err