public static synchronized StatFsHelper getInstance() {
    if (sStatsFsHelper == null) {
      sStatsFsHelper = new StatFsHelper();
    }
    return sStatsFsHelper;
  }
Helper class that periodically checks the amount of free space available.

<p>To keep the overhead low, it caches the free space information, and only updates that info
after two minutes.

<p>It is a singleton, and is thread-safe.

<p>Initialization is delayed until first use, so the first call to any method may incur some
additional cost.
fbcore/src/main/java/com/facebook/common/statfs/StatFsHelper.java