private void deleteOldItems() {
final int prevLength = length;
synchronized (requests) {
if (requests.size() > MAX_REQUESTS) {
requests.subList(0, DELTA_REQUESTS).clear();
final IoRequest first = requests.get(0);
final int start = first.getStart();
length = 0;
for (final IoRequest request : requests) {
request.setStart(request.getStart() - start);
length += request.getLength();
}