Add optional resource prefix support to "fake-mode"

Adding prefix (e.g. "fake_") to resource names has pros and cons.

With different resource name, real GPU workloads do not end on faked
devices, so one can easily run both real GPU plugin and workloads in
the same cluster with the fake ones.

However, GAS hard-codes resource names i.e. changing the name(s) with
a prefix will break GPU plugin resource management, so one should use
prefix only when fractional resources are not needed for faked
devices.

Signed-off-by: Eero Tamminen <eero.t.tamminen@intel.com>

cmd/gpu_plugin/gpu_plugin.go

@@ -55,6 +55,7 @@ const (
 
 type cliOptions struct {
 	preferredAllocationPolicy string
+	resourcePrefix            string
 	sharedDevNum              int
 	enableMonitoring          bool
 	resourceManagement        bool
@@ -176,7 +177,7 @@ func newDevicePlugin(sysfsDir, devfsDir string, options cliOptions) *devicePlugi
 	if options.resourceManagement {
 		var err error
 
-		dp.resMan, err = rm.NewResourceManager(monitorID, namespace+"/"+deviceType)
+		dp.resMan, err = rm.NewResourceManager(monitorID, namespace+"/"+options.resourcePrefix+deviceType)
 		if err != nil {
 			klog.Errorf("Failed to create resource manager: %+v", err)
 			return nil
@@ -330,7 +331,8 @@ func (dp *devicePlugin) scan() (dpapi.DeviceTree, error) {
 			}
 
 			if dp.options.enableMonitoring {
-				klog.V(4).Infof("Adding %s to GPU %s/%s", devPath, monitorType, monitorID)
+				klog.V(4).Infof("Adding %s to GPU resource %s%s/%s", devPath,
+					dp.options.resourcePrefix, monitorType, monitorID)
 
 				monitor = append(monitor, devSpec)
 			}
@@ -343,7 +345,7 @@ func (dp *devicePlugin) scan() (dpapi.DeviceTree, error) {
 				devID := fmt.Sprintf("%s-%d", f.Name(), i)
 				// Currently only one device type (i915) is supported.
 				// TODO: check model ID to differentiate device models.
-				devTree.AddDevice(deviceType, devID, deviceInfo)
+				devTree.AddDevice(dp.options.resourcePrefix+deviceType, devID, deviceInfo)
 
 				rmDevInfos[devID] = rm.NewDeviceInfo(nodes, nil, nil)
 			}
@@ -352,7 +354,7 @@ func (dp *devicePlugin) scan() (dpapi.DeviceTree, error) {
 	// all Intel GPUs are under single monitoring resource
 	if len(monitor) > 0 {
 		deviceInfo := dpapi.NewDeviceInfo(pluginapi.Healthy, monitor, nil, nil, nil)
-		devTree.AddDevice(monitorType, monitorID, deviceInfo)
+		devTree.AddDevice(dp.options.resourcePrefix+monitorType, monitorID, deviceInfo)
 	}
 
 	if dp.resMan != nil {
@@ -371,10 +373,10 @@ func (dp *devicePlugin) Allocate(request *pluginapi.AllocateRequest) (*pluginapi
 }
 
 func main() {
-	var prefix string
+	var faked string
 	var opts cliOptions
 
-	flag.StringVar(&fprefix, "fake-mode", "", "Prefix for devfs & sysfs paths")
+	flag.StringVar(&faked, "fake-mode", "", "Comma separated prefix for devfs & sysfs paths + prefix for resources names")
 	flag.BoolVar(&opts.enableMonitoring, "enable-monitoring", false, "whether to enable 'i915_monitoring' (= all GPUs) resource")
 	flag.BoolVar(&opts.resourceManagement, "resource-manager", false, "fractional GPU resource management")
 	flag.IntVar(&opts.sharedDevNum, "shared-dev-num", 1, "number of containers sharing the same GPU device")
@@ -400,12 +402,21 @@ func main() {
 	klog.V(1).Infof("GPU device plugin started with %s preferred allocation policy", opts.preferredAllocationPolicy)
 
 	var sysfs, devfs string
-	if prefix != "" {
-		sysfs = prefix + sysfsDrmDirectory
-		devfs = prefix + devfsDriDirectory
+	if faked != "" {
+		prefixes := strings.Split(faked, ",")
+		if len(prefixes) != 2 {
+			klog.Fatalf("%d commas in fake-mode option value, not one", len(prefixes)-1)
+		}
+		sysfs = prefixes[0] + sysfsDrmDirectory
+		devfs = prefixes[0] + devfsDriDirectory
+		opts.resourcePrefix = prefixes[1]
+		if opts.resourceManagement && opts.resourcePrefix != "" {
+			klog.Warning("Resource name prefix breaks resource management as it hard-codes their names")
+		}
 	} else {
 		sysfs = sysfsDrmDirectory
 		devfs = devfsDriDirectory
+		opts.resourcePrefix = ""
 	}
 	plugin := newDevicePlugin(sysfs, devfs, opts)
 	manager := dpapi.NewManager(namespace, plugin)