Re: BUG #14830: Missed NOTIFications, PostgreSQL 9.1.24

I wrote:
> Concretely, I suggest the attached patch. I tried Marko's testbed
> against this, and it seems indeed a bit faster than before ---
> running it for 100000 notifies takes about 19.25 seconds, rather than
> 19.5 seconds with HEAD. But the testbed is probably about the best
> case because it has a bunch of threads sending notifies to one
> receiver, so that the receiver is quite likely to have multiple
> messages to read at a time. OTOH, in a situation where the NOTIFY
> traffic isn't so high, it probably hardly matters anyway.

It occurred to me that it's easy to measure the worst case, ie always
one message per notify interrupt:

$ cat bnch.txt
LISTEN foo\; NOTIFY foo;
$ pgbench -n -c 1 -T 10 -f bnch.txt

On this case it seems that the patch is circa 2% slower than HEAD,
though that's only barely above the noise level in my measurements.
I think that's probably acceptable.

regards, tom lane