This seems very (very) strange to me. Did a simplified mockup in Java using a ConcurrentLinkedDeque. Got an absolute speed-up of ~8 going from 1 thread to 2 (or

This seems very (very) strange to me. Did a simplified mockup in Java using a ConcurrentLinkedDeque. Got an absolute speed-up of ~8 going from 1 thread to 2 (or 4)...and that's on a laptop. Did you perhaps measure CPU time rather than wall clock or push entries scaled by the number of threads? Didn't find your test source on GitHub..