Re: Estimating HugePages Requirements?

On Mon, Apr 25, 2022 at 2:15 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:

> On Fri, Apr 22, 2022 at 09:49:34AM +0200, Magnus Hagander wrote:
> > I agree that thats a very narrow use case. And I'm not sure the use case
> of
> > a running server is even that important here - it's really the offline
> one
> > that's important. Or rather, the really compelling one is when there is a
> > server running but I want to check the value offline because it will
> > change. SHOW doesn't help there because it shows the value based on the
> > currently running configuration, not the new one after a restart.
>
> You mean the case of a server where one would directly change
> postgresql.conf on a running server, and use postgres -C to see how
> much the kernel settings need to be changed before the restart?
>

Yes.

AIUI that was the original use-case for this feature. It certainly was for
me :)

> Hmm. So what's the solution on windows? I guess maybe it's not as
> important
> > there because there is no limit on huge pages, but generally getting the
> > expected shared memory usage might be useful? Just significantly less
> > important.
>
> Contrary to Linux, we don't need to care about the number of large
> pages that are necessary because there is no equivalent of
> vm.nr_hugepages on Windows (see [1]), do we? If that were the case,
> we'd have a use case for huge_page_size, additionally.
>

Right, for this one in particular -- that's what I meant with my comment
about there not being a limit. But this feature works for other settings as
well, not just the huge pages one. Exactly what the use-cases are can
vary, but surely they would have the same problems wrt redirects?

--
Magnus Hagander
Me: https://www.hagander.net/ <http://www.hagander.net/>
Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>