Re: Unportable implementation of background worker start

On 2017-04-20 20:10:41 -0400, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > On 2017-04-20 20:05:02 -0400, Tom Lane wrote:
> >> Also, if it's not there we'd fall back to using plain poll(), which is
> >> not so awful that we need to work hard to avoid it. I'd just as soon
> >> keep the number of combinations down.
>
> > Just using fcntl(SET, CLOEXEC) wound't increase the number of
> > combinations?
>
> True, if you just did it that way unconditionally. But doesn't that
> require an extra kernel call per CreateWaitEventSet()?

It does - the question is whether that matters much. FE/BE uses a
persistent wait set, but unfortunately much of other latch users
don't. And some of them can be somewhat frequent - so I guess that'd
possibly be measurable. Ok, so I'm on board with epoll1.

If somebody were to change more frequent latch users to use persistent
wait sets, that'd be good too.

- Andres