String.format("%s costs %d avail %d (%s)", chain.getClass().getName(), cost, this.credits.availablePermits(), this.name));
                }
                if ( ( next == null || chain.allowChain(next) ) && totalSize + size < maxSize && this.credits.tryAcquire(cost) ) {
                    totalSize += size;
                    last = chain;
                    chain = next;
                }