Re: Issue with the PRNG used by Postgres

Andres Freund <andres(at)anarazel(dot)de> writes:
> I think it could exascerbate the issue. Parag reported ~7k connections on a
> 128 core machine. The buffer replacement logic in < 16 tries to lock the old
> and new lock partitions at once. That can lead to quite bad "chains" of
> dependent lwlocks, occasionally putting all the pressure on a single lwlock.
> With 7k waiters on a single spinlock, higher frequency of wakeups will make it
> much more likely that the process holding the spinlock will be put to sleep.
> This is greatly exacerbated by the issue fixed in a4adc31f690, once the
> waitqueue is long, the spinlock will be held for an extended amount of time.

Yeah. So what's the conclusion? Leave it alone? Commit to
HEAD only?

regards, tom lane