Why ThreadHints.onSpinWait() is not added for SleepingWaitStrategy

[justinplus]

Hi,

Just noticed that ThreadHints.onSpinWait() is not added for SleepingWaitStrategy.
https://github.com/LMAX-Exchange/disruptor/blob/master/src/main/java/com/lmax/disruptor/SleepingWaitStrategy.java#L83

private int applyWaitMethod(final SequenceBarrier barrier, int counter)
        throws AlertException
    {
        barrier.checkAlert();

        if (counter > 100)
        {
            --counter;
            // added
            ThreadHints.onSpinWait()
        }
...

Is this intended?

Thank you,
Justin

[Palmr]

Hi Justin,

This is a fair question, and one I don't think anyone has an answer for.
I looked around the codebase and many implementations of WaitStrategy have a busy-spin component where the thread hint could be applied.

While the code compiles and runs with the thread hint in what seem like appropriate places, I think we would need a benchmark to prove they provide some benefit and more importantly that they don't come at a cost.

I will leave this ticket open as benchmarks are something currently being worked upon in the Disruptor, and I would welcome any benchmarks or experimental data on this in the mean time.

Thanks,
Nick