Add MaxBackground as tunable setting in fuse.MountOptions.

fuse/api.go

@@ -98,6 +98,9 @@ type FileSystemOptions struct {
 
 type MountOptions struct {
 	AllowOther bool
+
+	// Default is _DEFAULT_BACKGROUND_TASKS, 12.
+	MaxBackground int
 }
 
 // DefaultFileSystem implements a FileSystem that returns ENOSYS for every operation.

fuse/mountstate.go

@@ -33,6 +33,7 @@ type MountState struct {
 
 	*LatencyMap
 
+	opts *MountOptions
 	kernelSettings InitIn
 }
 
@@ -46,9 +47,15 @@ func (me *MountState) MountPoint() string {
 
 // Mount filesystem on mountPoint.
 func (me *MountState) Mount(mountPoint string, opts *MountOptions) os.Error {
+	if opts == nil {
+		opts = &MountOptions{
+			MaxBackground: _DEFAULT_BACKGROUND_TASKS,
+		}
+	}
+	me.opts = opts
 	
 	optStr := ""
-	if opts != nil && opts.AllowOther {
+	if opts.AllowOther {
 		optStr = "allow_other"
 	}
 
@@ -150,7 +157,7 @@ func (me *MountState) Loop(threaded bool) {
 	// This means that the request once read does not need to be
 	// assigned to another thread, so it avoids a context switch.
 	if threaded {
-		for i := 0; i < _BACKGROUND_TASKS; i++ {
+		for i := 0; i < me.opts.MaxBackground-1; i++ {
 			go me.loop()
 		}
 	}

fuse/opcode.go

@@ -84,8 +84,8 @@ func doInit(state *MountState, req *request) {
 		MaxReadAhead:        input.MaxReadAhead,
 		Flags:               state.kernelSettings.Flags,
 		MaxWrite:            maxRead,
-		CongestionThreshold: _BACKGROUND_TASKS * 3 / 4,
-		MaxBackground:       _BACKGROUND_TASKS,
+		CongestionThreshold: uint16(state.opts.MaxBackground * 3 / 4),
+		MaxBackground:       uint16(state.opts.MaxBackground),
 	}
 
 	req.outData = unsafe.Pointer(out)

fuse/types.go

@@ -35,8 +35,7 @@ const (
 )
 
 const (
-	// TODO - we should read this from /sys/fs/fuse/ , dynamically.
-	_BACKGROUND_TASKS = 12
+	_DEFAULT_BACKGROUND_TASKS = 12
 )
 
 type Status int32