What is the fastest cyclic synchronization in Java (ExecutorService vs. CyclicBarrier vs. X)?

Question

Which Java synchronization construct is likely to provide the best performance for a concurrent, iterative processing scenario with a fixed number of threads like the one outli

Answer 1

Update: V5 - Busy Wait in all threads (seems optimal so far)

Since all cores are dedicated to this task, it seemed worth a try to simply eliminate all the complex synchronization constructs and do a busy wait at each synchronization point in all threads. This turns out to beat all other approaches by a wide margin.

The setup is as follows: start with V4 above (CyclicBarrier + Busy Wait). Replace the CyclicBarrier with an AtomicInteger that the main thread resets to zero each cycle. Each worker thread Runnable that completes its work increments the atomic integer by one. The main thread busy waits:

while( true ) {
    // busy-wait for threads to complete their work
    if( atomicInt.get() >= workerThreadCount ) break;
}

Instead of 8, only 7 worker threads are launched (since all threads, including the main thread, now load a core pretty much completely). The results are as follows:

blocksize | system | user | cycles/sec
256k        1.0%     98%       1.36
64k         1.0%     98%       6.8
16k         1.0%     98%      44.6
4096        1.0%     98%     354
1024        1.0%     98%    1189
256         1.0%     98%    3222
64          1.5%     98%    8333
16          2.0%     98%   16129

Using a wait/notify in the worker threads reduces the throughput to about 1/3rd of this solution.