Re: Draft for basic NUMA observability

On Thu, Mar 27, 2025 at 2:15 PM Álvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:

> Hello

Good morning :)

> I think you should remove numa_warn() and numa_error() from 0001.
> AFAICS they are dead code (even with all your patches applied), and
> furthermore would get you in trouble regarding memory allocation because
> src/port is not allowed to use palloc et al. If you wanted to keep them
> you'd have to have them in src/common, but looking at the rest of the
> code in that patch, ISTM src/port is the right place for it. If in the
> future you discover that you do need numa_warn(), you can create a
> src/common/ file for it then.

Understood, trimmed it out from the patch. I'm going to respond also
within minutes to Andres' review and I'm going to post a new version
(v17) there.

> Is pg_buffercache really the best place for these NUMA introspection
> routines? I'm not saying that it isn't, maybe we're okay with that
> (particularly if we can avoid duplicated code), but it seems a bit weird
> to me.

I think it is, because as I understand, Andres wanted to have
observability per single database *page* and to avoid code duplication
we are just putting it there (it's natural fit). Imagine looking up an
8kB root btree memory page being hit hard from CPUs on other NUMA
nodes (this just gives ability to see that, but you could of course
also get aggregation to get e.g. NUMA node balance for single relation
and so on).

-J.