if (RefCountSpace.RC_SANITY_CHECK) return true;
  private final boolean shouldAct(int thresholdPages) {    final int LOG_WRIGGLE = 2;    int slack = log2((int) Plan.getPagesAvail()/thresholdPages);    int mask = (1<<slack)-1;    boolean rtn = (slack <= LOG_WRIGGLE) && ((Plan.gcCount() & mask) == mask);    return rtn;  }