vz: add adaptive memory ballooning for macOS Virtualization Framework

cmd/lima-guestagent/daemon_linux.go

@@ -17,6 +17,7 @@ import (
 
 	"github.com/lima-vm/lima/v2/pkg/guestagent"
 	"github.com/lima-vm/lima/v2/pkg/guestagent/api/server"
+	"github.com/lima-vm/lima/v2/pkg/guestagent/metrics"
 	"github.com/lima-vm/lima/v2/pkg/guestagent/serialport"
 	"github.com/lima-vm/lima/v2/pkg/guestagent/ticker"
 	"github.com/lima-vm/lima/v2/pkg/portfwdserver"
@@ -145,5 +146,6 @@ func daemonAction(cmd *cobra.Command, _ []string) error {
 		logrus.Infof("serving the guest agent on %q", socket)
 	}
 	defer logrus.Debug("exiting lima-guestagent daemon")
-	return server.StartServer(ctx, l, &server.GuestServer{Agent: agent, TunnelS: portfwdserver.NewTunnelServer()})
+	collector := metrics.NewCollector()
+	return server.StartServer(ctx, l, &server.GuestServer{Agent: agent, TunnelS: portfwdserver.NewTunnelServer(), Collector: collector})
 }

pkg/driver/driver.go

@@ -77,6 +77,12 @@ type GuestAgent interface {
 	GuestAgentConn(_ context.Context) (net.Conn, string, error)
 }
 
+// Ballooner is an optional interface for drivers that support memory ballooning.
+// Use type assertion to check if a driver implements this interface.
+type Ballooner interface {
+	SetBalloonTarget(targetBytes uint64) error
+}
+
 // Driver interface is used by hostagent for managing vm.
 type Driver interface {
 	Lifecycle

pkg/driver/vz/vm_darwin.go

@@ -48,8 +48,9 @@ const diskImageCachingMode = vz.DiskImageCachingModeCached
 
 type virtualMachineWrapper struct {
 	*vz.VirtualMachine
-	mu      sync.Mutex
-	stopped bool
+	mu            sync.Mutex
+	stopped       bool
+	balloonDevice *vz.VirtioTraditionalMemoryBalloonDevice
 }
 
 // Hold all *os.File created via socketpair() so that they won't get garbage collected. f.FD() gets invalid if f gets garbage collected.
@@ -72,6 +73,15 @@ func startVM(ctx context.Context, inst *limatype.Instance, sshLocalPort int, onV
 	}
 
 	wrapper := &virtualMachineWrapper{VirtualMachine: machine, stopped: false}
+
+	// Capture the balloon device reference for runtime memory control.
+	for _, dev := range machine.MemoryBalloonDevices() {
+		if bd := vz.AsVirtioTraditionalMemoryBalloonDevice(dev); bd != nil {
+			wrapper.balloonDevice = bd
+			break
+		}
+	}
+
 	notifySSHLocalPortAccessible := make(chan any)
 	sendErrCh := make(chan error)
 

pkg/driver/vz/vz_driver_darwin.go

@@ -207,6 +207,32 @@ func (l *LimaVzDriver) FillConfig(ctx context.Context, cfg *limatype.LimaYAML, _
 		}
 	}
 
+	// Memory balloon defaults — only set when enabled.
+	if vzOpts.MemoryBalloon.Enabled == nil {
+		vzOpts.MemoryBalloon.Enabled = ptr.Of(false)
+	}
+	if *vzOpts.MemoryBalloon.Enabled {
+		if vzOpts.MemoryBalloon.Min == nil {
+			// 25% of configured memory.
+			if cfg.Memory != nil {
+				if memBytes, err := units.RAMInBytes(*cfg.Memory); err == nil {
+					vzOpts.MemoryBalloon.Min = ptr.Of(units.BytesSize(float64(memBytes) * 0.25))
+				}
+			}
+		}
+		if vzOpts.MemoryBalloon.IdleTarget == nil {
+			// 33% of configured memory.
+			if cfg.Memory != nil {
+				if memBytes, err := units.RAMInBytes(*cfg.Memory); err == nil {
+					vzOpts.MemoryBalloon.IdleTarget = ptr.Of(units.BytesSize(float64(memBytes) * 0.33))
+				}
+			}
+		}
+		if vzOpts.MemoryBalloon.Cooldown == nil {
+			vzOpts.MemoryBalloon.Cooldown = ptr.Of("30s")
+		}
+	}
+
 	var opts any
 	if err := limayaml.Convert(vzOpts, &opts, ""); err != nil {
 		logrus.WithError(err).Warnf("Couldn't convert %+v", vzOpts)
@@ -536,6 +562,21 @@ func (l *LimaVzDriver) GuestAgentConn(_ context.Context) (net.Conn, string, erro
 	return nil, "", errors.New("unable to connect to guest agent via vsock port 2222")
 }
 
+// SetBalloonTarget adjusts the balloon device to set the target memory size in bytes.
+// The balloon inflates or deflates to control memory available to the guest.
+func (l *LimaVzDriver) SetBalloonTarget(targetBytes uint64) error {
+	if l.machine == nil {
+		return errors.New("vz: VM is not running")
+	}
+	l.machine.mu.Lock()
+	defer l.machine.mu.Unlock()
+	if l.machine.balloonDevice == nil {
+		return errors.New("vz: no balloon device available")
+	}
+	l.machine.balloonDevice.SetTargetVirtualMachineMemorySize(targetBytes)
+	return nil
+}
+
 func (l *LimaVzDriver) Info() driver.Info {
 	var info driver.Info
 

pkg/guestagent/api/client/client.go

@@ -89,3 +89,8 @@ func (c *GuestAgentClient) SyncTime(ctx context.Context, hostTime time.Time) (*a
 	}
 	return c.cli.SyncTime(ctx, req)
 }
+
+// GetMemoryMetrics retrieves guest memory statistics for the balloon controller.
+func (c *GuestAgentClient) GetMemoryMetrics(ctx context.Context) (*api.MemoryMetrics, error) {
+	return c.cli.GetMemoryMetrics(ctx, &emptypb.Empty{})
+}

pkg/guestagent/api/guestservice.pb.desc

@@ -1,5 +1,5 @@
 
-ã
+©
 guestservice.protogoogle/protobuf/empty.protogoogle/protobuf/timestamp.proto"0
 Info(
 local_ports
 (2.IPPortR
@@ -29,10 +29,30 @@ guest_addr 
(	R	guestAddr&
 TimeSyncResponse
 adjusted
 
(Radjusted
 drift_ms 
(RdriftMs
-error 
(	Rerror2ù

+error 
(	Rerror"‡
+MemoryMetrics&
+mem_total_bytes
 
(RmemTotalBytes.
+mem_available_bytes 
(RmemAvailableBytes(
+mem_cached_bytes 
(RmemCachedBytes(
+swap_total_bytes 
(RswapTotalBytes&
+swap_free_bytes 
(RswapFreeBytes$
+anon_rss_bytes 
(RanonRssBytes+
+psi_memory_some_10 
(
RpsiMemorySome10+
+psi_memory_full_10 
(
RpsiMemoryFull100
+swap_in_bytes_per_sec	 
(
RswapInBytesPerSec2
+swap_out_bytes_per_sec
+ 
(
RswapOutBytesPerSec&
+page_fault_rate 
(
RpageFaultRate'
+container_count 
(RcontainerCount2
+container_cpu_percent 
(
RcontainerCpuPercent:
+container_io_bytes_per_sec 
(
RcontainerIoBytesPerSec!
+oom_detected 
(RoomDetected+
+psi_memory_some_60 
(
RpsiMemorySome60+
+psi_memory_full_60 
(
RpsiMemoryFull602µ
 GuestService(
 GetInfo.google.protobuf.Empty.Info-
 	GetEvents.google.protobuf.Empty.Event0
1
 PostInotify.Inotify.google.protobuf.Empty(
,
 Tunnel.TunnelMessage.TunnelMessage(
0
/
-SyncTime.TimeSyncRequest.TimeSyncResponseB/Z-github.com/lima-vm/lima/v2/pkg/guestagent/apibproto3
+SyncTime.TimeSyncRequest.TimeSyncResponse:
+GetMemoryMetrics.google.protobuf.Empty.MemoryMetricsB/Z-github.com/lima-vm/lima/v2/pkg/guestagent/apibproto3