mount: limit background requests and congestion threshold

weed/command/mount_std.go

@@ -150,6 +150,8 @@ func RunMount(option *MountOptions, umask os.FileMode) bool {
 		fuse.MaxReadahead(1024 * 128),
 		fuse.AsyncRead(),
 		fuse.WritebackCache(),
+		fuse.MaxBackground(128),
+		fuse.CongestionThreshold(128),
 	}
 
 	options = append(options, osSpecificMountOptions()...)