public void commitToDisk() {
    if (usingAllThreads()) {
        // get current paused count
        Shard pausedShard = getAndPauseRandomShard(); // free up a cpu core by pausing a shard
        world.commitToDisk();
        if (pausedShard != null) {
            pausedShard.isPaused = false;
        }
    } else {
        world.commitToDisk();
    }
}