protected Integer initialValue() {
            return idx.getAndIncrement();
        }
This is a bit annoying, I need the threads to keep their queues, so each thread needs an index. The id
is used to pick the in/out queues.
jctools-benchmarks/src/main/java/org/jctools/jmh/latency/spsc/RingCqBurstRoundTripWithGroups.java