code: public void clearUnused(ConfigImpl config) {
  
  	SystemOut.printDate(config.getOutWriter(), "PagePool: " + size() + ">(" + maxSize + ")");
  	if (size() > maxSize) {
  	    String[] keys = keys();
  	    LongKeyList list = new LongKeyList();
  	    for (int i = 0; i < keys.length; i++) {
  		PageSource ps = getPageSource(keys[i], false);
  		long updateTime = ps.getLastAccessTime();
  		if (updateTime + timeout < System.currentTimeMillis()) {
  		    long add = ((ps.getAccessCount() - 1) * 10000);
  		    if (add > timeout) add = timeout;
  		    list.add(updateTime + add, keys[i]);
  		}
  	    }
  	    while (size() > maxSize) {
  		Object key = list.shift();
  		if (key == null) break;
  		remove(key.toString());
  	    }
  	}
      }
docs: clear unused pages from page pool