Bruce Momjian wrote:
> My guess is the existing behavior was designed to allow waking of
> multiple waiters _sometimes_ without starving of exclusive waiters.
Well, I think the current algorithm *does* allow starvation, at least in
some situations. Consider a workload in which a new shared reader
arrives every 50 ms, and holds the lock for, say, 500 ms. If an
exclusive waiter arrives, they will starve with the current algorithm.
> There should be a comment in the code explaining this usage and I bet it
> was intentional.
Oh, I bet it was intentional as well :) I'm mostly curious to see
exactly what the reasoning was, and whether it is necessary that we
preserve the FIFO behavior while considering optimizations.
-Neil