neonvm: sysfs cpu state based scaling support

introduce separate CPU scaling flow based on the vmSpec.cpuScalingMode

If vmSpec.cpuScalingMode is equal to `qmp_scaling` the logic of the
scaling is preserved as before:

- Scale, if required the amount of CPUs using qmp commands.
- If it is required to scale cgroups, call vm-runner /cpu_change endpoint

if vmSpec.cpuScalingMode is equal to `cpuSysfsStateScaling` all cpu
scaling requests go directly to the vm-runner /cpu_change, which in
that configuration goes to the neonvm-daemon to reconcile required
amount of online CPUs.

Value `cpuSysfsStateScaling` also modifies the qemu and the kernel
arguments to enable plug all CPUs but mark as online only first one.

Signed-off-by: Misha Sakhnov <[email protected]>

Makefile

@@ -133,9 +133,10 @@ test: fmt vet envtest ## Run tests.
 
 .PHONY: build
 build: fmt vet bin/vm-builder ## Build all neonvm binaries.
-	GOOS=linux go build -o bin/controller       neonvm/main.go
-	GOOS=linux go build -o bin/vxlan-controller neonvm/tools/vxlan/controller/main.go
-	GOOS=linux go build -o bin/runner           neonvm/runner/*.go
+	GOOS=linux go build -o bin/controller       neonvm-controller/cmd/main.go
+	GOOS=linux go build -o bin/vxlan-controller neonvm-vxlan-controller/cmd/main.go
+	GOOS=linux go build -o bin/daemon           neonvm-daemon/main.go
+	GOOS=linux go build -o bin/runner           neonvm-runner/cmd/main.go
 
 .PHONY: bin/vm-builder
 bin/vm-builder: ## Build vm-builder binary.

neonvm-controller/cmd/main.go

@@ -95,7 +95,7 @@ func main() {
 	var concurrencyLimit int
 	var skipUpdateValidationFor map[types.NamespacedName]struct{}
 	var disableRunnerCgroup bool
-	var useOnlineOfflining bool
+	var useCpuSysfsStateScaling bool
 	var qemuDiskCacheSettings string
 	var defaultMemoryProvider vmv1.MemoryProvider
 	var memhpAutoMovableRatio string
@@ -106,7 +106,6 @@ func main() {
 	flag.BoolVar(&enableLeaderElection, "leader-elect", false,
 		"Enable leader election for controller manager. "+
 			"Enabling this will ensure there is only one active controller manager.")
-	flag.BoolVar(&useOnlineOfflining, "use-online-offlining", false, "Use online offlining for CPU scaling")
 	flag.IntVar(&concurrencyLimit, "concurrency-limit", 1, "Maximum number of concurrent reconcile operations")
 	flag.Func(
 		"skip-update-validation-for",
@@ -134,6 +133,7 @@ func main() {
 			return nil
 		},
 	)
+	flag.BoolVar(&useCpuSysfsStateScaling, "use-cpu-sysfs-state-scaling", false, "Use sysfs cpu state scaling for CPU scaling")
 	flag.BoolVar(&disableRunnerCgroup, "disable-runner-cgroup", false, "Disable creation of a cgroup in neonvm-runner for fractional CPU limiting")
 	flag.StringVar(&qemuDiskCacheSettings, "qemu-disk-cache-settings", "cache=none", "Set neonvm-runner's QEMU disk cache settings")
 	flag.Func("default-memory-provider", "Set default memory provider to use for new VMs", defaultMemoryProvider.FlagFunc)
@@ -189,7 +189,7 @@ func main() {
 	reconcilerMetrics := controllers.MakeReconcilerMetrics()
 
 	rc := &controllers.ReconcilerConfig{
-		UseOnlineOfflining:      useOnlineOfflining,
+		DisableRunnerCgroup:     disableRunnerCgroup,
 		MaxConcurrentReconciles: concurrencyLimit,
 		SkipUpdateValidationFor: skipUpdateValidationFor,
 		QEMUDiskCacheSettings:   qemuDiskCacheSettings,

neonvm-controller/deployment.yaml

@@ -55,7 +55,6 @@ spec:
         - "--concurrency-limit=128"
         - "--skip-update-validation-for="
         - "--disable-runner-cgroup"
-        - "--use-online-offlining"        
         # See #775 and its links.
         # * cache.writeback=on - don't set O_DSYNC (don't flush every write)
         # * cache.direct=on    - use O_DIRECT (don't abuse host's page cache!)

neonvm-daemon/cmd/main.go

@@ -4,15 +4,16 @@ import (
 	"flag"
 	"fmt"
 	"io"
-	"math"
 	"net/http"
 	"os"
 	"strconv"
 	"sync"
 	"time"
 
-	"github.com/neondatabase/autoscaling/neonvm/daemon/pkg/cpuscaling"
 	"go.uber.org/zap"
+
+	vmv1 "github.com/neondatabase/autoscaling/neonvm/apis/neonvm/v1"
+	"github.com/neondatabase/autoscaling/pkg/neonvm/cpuscaling"
 )
 
 func main() {
@@ -31,8 +32,9 @@ func main() {
 	defer logger.Sync() //nolint:errcheck // what are we gonna do, log something about it?
 
 	logger.Info("Starting neonvm-daemon", zap.String("addr", *addr))
-	cpuHotPlugController := &cpuscaling.CPUOnlineOffliner{}
+	cpuHotPlugController := &cpuscaling.CPUSysFsStateScaler{}
 	srv := cpuServer{
+		cpuOperationsMutex:  &sync.Mutex{},
 		cpuSystemWideScaler: cpuHotPlugController,
 		logger:              logger.Named("cpu-srv"),
 	}
@@ -43,47 +45,29 @@ type cpuServer struct {
 	// Protects CPU operations from concurrent access to prevent multiple ensureOnlineCPUs calls from running concurrently
 	// and ensure that status response is always actual
 	cpuOperationsMutex  *sync.Mutex
-	cpuSystemWideScaler *cpuscaling.CPUOnlineOffliner
+	cpuSystemWideScaler *cpuscaling.CPUSysFsStateScaler
 	logger              *zap.Logger
 }
 
-// milliCPU is a type that represents CPU in milli units
-type milliCPU uint64
-
-// milliCPUFromString converts a byte slice to milliCPU
-func milliCPUFromString(s []byte) (milliCPU, error) {
-	cpu, err := strconv.ParseUint(string(s), 10, 32)
-	if err != nil {
-		return 0, err
-	}
-	return milliCPU(cpu), nil
-}
-
-// ToCPU converts milliCPU to CPU
-func (m milliCPU) ToCPU() int {
-	cpu := float64(m) / 1000.0
-	// Use math.Ceil to round up to the next CPU.
-	return int(math.Ceil(cpu))
-}
-
 func (s *cpuServer) handleGetCPUStatus(w http.ResponseWriter) {
+	// should be replaced with cgroups milliseconds to be exposed instead of having CPU
 	s.cpuOperationsMutex.Lock()
 	defer s.cpuOperationsMutex.Unlock()
-	totalCPUs, err := s.cpuSystemWideScaler.GetTotalCPUsCount()
-	if err != nil {
-		w.WriteHeader(http.StatusInternalServerError)
-		return
-	}
 	activeCPUs, err := s.cpuSystemWideScaler.GetActiveCPUsCount()
 	if err != nil {
 		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
-	w.Write([]byte(fmt.Sprintf("%d %d", activeCPUs, totalCPUs)))
 	w.WriteHeader(http.StatusOK)
+	if _, err := w.Write([]byte(fmt.Sprintf("%d", activeCPUs*1000))); err != nil {
+		s.logger.Error("could not write response", zap.Error(err))
+	}
 }
 
 func (s *cpuServer) handleSetCPUStatus(w http.ResponseWriter, r *http.Request) {
+	// TODO: should the call to this method be conditional, only if the statefs cpu scaling is enabled?
+	// on the other hand, currently this endpoint is called by runner only if the statefs scaling is enabled
+	// and it is a bit tricky to pass vmSpec here
 	s.cpuOperationsMutex.Lock()
 	defer s.cpuOperationsMutex.Unlock()
 	body, err := io.ReadAll(r.Body)
@@ -92,19 +76,20 @@ func (s *cpuServer) handleSetCPUStatus(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusBadRequest)
 		return
 	}
-
-	milliCPU, err := milliCPUFromString(body)
+	updateInt, err := strconv.Atoi(string(body))
+	update := vmv1.MilliCPU(updateInt)
 	if err != nil {
-		s.logger.Error("could not parse request body as uint32", zap.Error(err))
+		s.logger.Error("could not unmarshal request body", zap.Error(err))
 		w.WriteHeader(http.StatusBadRequest)
 		return
 	}
-	if err := s.cpuSystemWideScaler.EnsureOnlineCPUs(milliCPU.ToCPU()); err != nil {
-		s.logger.Error("failed to ensure online CPUs", zap.Error(err))
+	s.logger.Info("Setting CPU status", zap.String("body", string(body)))
+	if err := s.cpuSystemWideScaler.EnsureOnlineCPUs(int(update.RoundedUp())); err != nil {
+		s.logger.Error("could not ensure online CPUs", zap.Error(err))
 		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
-	w.WriteHeader(http.StatusNoContent)
+	w.WriteHeader(http.StatusOK)
 }
 
 func (s *cpuServer) run(addr string) {

neonvm-runner/cmd/main.go

@@ -616,7 +616,6 @@ type Config struct {
 	diskCacheSettings    string
 	memoryProvider       vmv1.MemoryProvider
 	autoMovableRatio     string
-	useOnlineOfflining   bool
 }
 
 func newConfig(logger *zap.Logger) *Config {
@@ -630,7 +629,6 @@ func newConfig(logger *zap.Logger) *Config {
 		diskCacheSettings:    "cache=none",
 		memoryProvider:       "", // Require that this is explicitly set. We'll check later.
 		autoMovableRatio:     "", // Require that this is explicitly set IFF memoryProvider is VirtioMem. We'll check later.
-		useOnlineOfflining:   false,
 	}
 	flag.StringVar(&cfg.vmSpecDump, "vmspec", cfg.vmSpecDump,
 		"Base64 encoded VirtualMachine json specification")
@@ -651,7 +649,6 @@ func newConfig(logger *zap.Logger) *Config {
 	flag.Func("memory-provider", "Set provider for memory hotplug", cfg.memoryProvider.FlagFunc)
 	flag.StringVar(&cfg.autoMovableRatio, "memhp-auto-movable-ratio",
 		cfg.autoMovableRatio, "Set value of kernel's memory_hotplug.auto_movable_ratio [virtio-mem only]")
-	flag.BoolVar(&cfg.useOnlineOfflining, "use-online-offlining", false, "Use online offlining for CPU scaling")
 	flag.Parse()
 
 	if cfg.memoryProvider == "" {
@@ -761,7 +758,7 @@ func run(logger *zap.Logger) error {
 
 	tg.Go("qemu-cmd", func(logger *zap.Logger) error {
 		var err error
-		qemuCmd, err = buildQEMUCmd(cfg, logger, vmSpec, &vmStatus, enableSSH, swapSize, hostname, cfg.useOnlineOfflining)
+		qemuCmd, err = buildQEMUCmd(cfg, logger, vmSpec, &vmStatus, enableSSH, swapSize, hostname)
 		return err
 	})
 
@@ -815,7 +812,6 @@ func buildQEMUCmd(
 	enableSSH bool,
 	swapSize *resource.Quantity,
 	hostname string,
-	useOnlineOfflining bool,
 ) ([]string, error) {
 	// prepare qemu command line
 	qemuCmd := []string{
@@ -893,21 +889,26 @@ func buildQEMUCmd(
 		logger.Warn("not using KVM acceleration")
 	}
 	qemuCmd = append(qemuCmd, "-cpu", "max")
-	if useOnlineOfflining {
-		// if we use online offlining we specify start cpus equal to max cpus
+
+	// cpu scaling details
+	maxCPUs := vmSpec.Guest.CPUs.Max.RoundedUp()
+	minCPUs := vmSpec.Guest.CPUs.Min.RoundedUp()
+
+	if vmSpec.CpuScalingMode != nil && *vmSpec.CpuScalingMode == vmv1.CpuScalingModeCpuSysfsState {
+		// if we use sysfs based scaling we specify start cpus equal to max cpus
 		qemuCmd = append(qemuCmd, "-smp", fmt.Sprintf(
 			"cpus=%d,maxcpus=%d,sockets=1,cores=%d,threads=1",
-			vmSpec.Guest.CPUs.Max.RoundedUp(),
-			vmSpec.Guest.CPUs.Max.RoundedUp(),
-			vmSpec.Guest.CPUs.Max.RoundedUp(),
+			maxCPUs,
+			maxCPUs,
+			maxCPUs,
 		))
 	} else {
 		// if we use hotplug we specify start cpus equal to min cpus and scale using udev rules for cpu plug events
 		qemuCmd = append(qemuCmd, "-smp", fmt.Sprintf(
 			"cpus=%d,maxcpus=%d,sockets=1,cores=%d,threads=1",
-			vmSpec.Guest.CPUs.Min.RoundedUp(),
-			vmSpec.Guest.CPUs.Max.RoundedUp(),
-			vmSpec.Guest.CPUs.Max.RoundedUp(),
+			minCPUs,
+			maxCPUs,
+			maxCPUs,
 		))
 	}
 
@@ -997,8 +998,8 @@ func makeKernelCmdline(cfg *Config, vmSpec *vmv1.VirtualMachineSpec, vmStatus *v
 	if cfg.appendKernelCmdline != "" {
 		cmdlineParts = append(cmdlineParts, cfg.appendKernelCmdline)
 	}
-	if cfg.useOnlineOfflining {
-		// if we use online offlining we need to specify the start cpus as min CPUs
+	if vmSpec.CpuScalingMode != nil && *vmSpec.CpuScalingMode == vmv1.CpuScalingModeCpuSysfsState {
+		// if we use sysfs based scaling we need to specify the start cpus as min CPUs
 		cmdlineParts = append(cmdlineParts, fmt.Sprintf("maxcpus=%d", vmSpec.Guest.CPUs.Min.RoundedUp()))
 	}
 
@@ -1047,8 +1048,12 @@ func runQEMU(
 	wg := sync.WaitGroup{}
 
 	wg.Add(1)
+	useCpuSysfsStateScaling := false
+	if vmSpec.CpuScalingMode != nil && *vmSpec.CpuScalingMode == vmv1.CpuScalingModeCpuSysfsState {
+		useCpuSysfsStateScaling = true
+	}
 	go terminateQemuOnSigterm(ctx, logger, &wg)
-	if !cfg.skipCgroupManagement || cfg.enableDummyCPUServer {
+	if !cfg.skipCgroupManagement || cfg.enableDummyCPUServer || useCpuSysfsStateScaling {
 		var callbacks cpuServerCallbacks
 
 		if cfg.enableDummyCPUServer {
@@ -1060,6 +1065,13 @@ func runQEMU(
 					return lo.ToPtr(vmv1.MilliCPU(lastValue.Load())), nil
 				},
 				set: func(logger *zap.Logger, cpu vmv1.MilliCPU) error {
+					if useCpuSysfsStateScaling {
+						err := setNeonvmDaemonCPU(cpu)
+						if err != nil {
+							logger.Error("setting CPU through NeonVM Daemon failed", zap.Any("cpu", cpu), zap.Error(err))
+							return err
+						}
+					}
 					lastValue.Store(uint32(cpu))
 					return nil
 				},
@@ -1830,3 +1842,33 @@ func overlayNetwork(iface string) (mac.MAC, error) {
 
 	return mac, nil
 }
+
+func setNeonvmDaemonCPU(cpu vmv1.MilliCPU) error {
+	_, vmIP, _, err := calcIPs(defaultNetworkCIDR)
+	if err != nil {
+		return fmt.Errorf("could not calculate VM IP address: %w", err)
+	}
+
+	ctx, cancel := context.WithTimeout(context.TODO(), time.Second)
+	defer cancel()
+
+	url := fmt.Sprintf("http://%s:25183/cpu", vmIP)
+	body := bytes.NewReader([]byte(fmt.Sprintf("%d", uint32(cpu))))
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPut, url, body)
+	if err != nil {
+		return fmt.Errorf("could not build request: %w", err)
+	}
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("could not send request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return fmt.Errorf("neonvm-daemon responded with status %d", resp.StatusCode)
+	}
+
+	return nil
+}

pkg/neonvm/controllers/config.go

@@ -11,11 +11,6 @@ import (
 // ReconcilerConfig stores shared configuration for VirtualMachineReconciler and
 // VirtualMachineMigrationReconciler.
 type ReconcilerConfig struct {
-	// UseOnlineOfflining, if true, enables using online offlining for new VM runner pods instead of QMP cpu hotplugging.
-	//
-	// This is defined as a config option so we can do a gradual rollout of this change.
-	UseOnlineOfflining bool
-
 	// DisableRunnerCgroup, if true, disables running QEMU in a cgroup in new VM runner pods.
 	// Fractional CPU scaling will continue to *pretend* to work, but it will not do anything in
 	// practice.