return new Builder<K, V>();
  }

  public static final class Builder<K, V> extends ImmutableMap.Builder<K, V> {

    public Builder() {}

    Builder(int initCapacity) {
      super(initCapacity);
    }

    @CanIgnoreReturnValue
    @Override
    public Builder<K, V> put(K key, V value) {
      super.put(key, value);
      return this;
    }

    @CanIgnoreReturnValue

		// pf_c = (f_i + x)/c_i,
		// pf_c - percentage free space across pools, f_i - ith pool's free space, c_i - ith pool's capacity
		// i.e. x = c_i*pfc -f_i
		totalBytesToRebal := float64(ps.InitCapacity)*meta.PercentFreeGoal - float64(ps.InitFreeSpace)
		elapsed := time.Since(ps.Info.StartTime)
		eta := time.Duration(totalBytesToRebal * float64(elapsed) / float64(ps.Bytes))
		if !ps.Info.EndTime.IsZero() {