  A number of concurrent, relaxed priority queues have recently been proposed
and implemented. Results are commonly reported for a throughput benchmark that
uses a uniform distribution of keys drawn from a large integer range, and
mostly for single systems. We have conducted more extensive benchmarking of
three recent, relaxed priority queues on four different types of systems with
different key ranges and distributions. While we can show superior throughput
and scalability for our own k-LSM priority queue for the uniform key
distribution, the picture changes drastically for other distributions, both
with respect to achieved throughput and relative merit of the priority queues.
The throughput benchmark alone is thus not sufficient to characterize the
performance of concurrent priority queues. Our benchmark code and k-LSM
priority queue are publicly available to foster future comparison.
