platform: Improve OOM killer for iOS

service/oomkiller/service_stub.go

@@ -7,33 +7,75 @@ import (
 
 	"github.com/sagernet/sing-box/adapter"
 	boxService "github.com/sagernet/sing-box/adapter/service"
-	C "github.com/sagernet/sing-box/constant"
+	boxConstant "github.com/sagernet/sing-box/constant"
 	"github.com/sagernet/sing-box/log"
 	"github.com/sagernet/sing-box/option"
 	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/memory"
+	"github.com/sagernet/sing/service"
 )
 
 func RegisterService(registry *boxService.Registry) {
-	boxService.Register[option.OOMKillerServiceOptions](registry, C.TypeOOMKiller, NewService)
+	boxService.Register[option.OOMKillerServiceOptions](registry, boxConstant.TypeOOMKiller, NewService)
 }
 
 type Service struct {
 	boxService.Adapter
+	logger        log.ContextLogger
+	router        adapter.Router
+	adaptiveTimer *adaptiveTimer
+	timerConfig   timerConfig
+	hasTimerMode  bool
+	useAvailable  bool
+	memoryLimit   uint64
 }
 
 func NewService(ctx context.Context, logger log.ContextLogger, tag string, options option.OOMKillerServiceOptions) (adapter.Service, error) {
-	return &Service{
-		Adapter: boxService.NewAdapter(C.TypeOOMKiller, tag),
-	}, nil
+	s := &Service{
+		Adapter: boxService.NewAdapter(boxConstant.TypeOOMKiller, tag),
+		logger:  logger,
+		router:  service.FromContext[adapter.Router](ctx),
+	}
+
+	if options.MemoryLimit != nil {
+		s.memoryLimit = options.MemoryLimit.Value()
+	}
+	if s.memoryLimit > 0 {
+		s.hasTimerMode = true
+	} else if memory.AvailableSupported() {
+		s.useAvailable = true
+		s.hasTimerMode = true
+	}
+
+	config, err := buildTimerConfig(options, s.memoryLimit, s.useAvailable)
+	if err != nil {
+		return nil, err
+	}
+	s.timerConfig = config
+
+	return s, nil
 }
 
 func (s *Service) Start(stage adapter.StartStage) error {
 	if stage != adapter.StartStateStart {
 		return nil
 	}
-	return E.New("memory pressure monitoring is not available on this platform")
+	if !s.hasTimerMode {
+		return E.New("memory pressure monitoring is not available on this platform without memory_limit")
+	}
+	s.adaptiveTimer = newAdaptiveTimer(s.logger, s.router, s.timerConfig)
+	s.adaptiveTimer.start(0)
+	if s.useAvailable {
+		s.logger.Info("started memory monitor with available memory detection")
+	} else {
+		s.logger.Info("started memory monitor with limit: ", s.memoryLimit/(1024*1024), " MiB")
+	}
+	return nil
 }
 
 func (s *Service) Close() error {
+	if s.adaptiveTimer != nil {
+		s.adaptiveTimer.stop()
+	}
 	return nil
 }