consumes energy when idle


cpu profiling result.
![default](https://cloud.githubusercontent.com/assets/1230701/25388072/582bad26-29ff-11e7-8d90-f4703ca3fa3a.png)

![default](https://cloud.githubusercontent.com/assets/1230701/25388134/836a8a16-29ff-11e7-86c8-655ed98af425.png)

linter consumes energy without any operation.
