Re: effective_cache_size

A follow-up on this:

Should documentation also mention that it does not make sense to set
effective_cache_size < shared_buffers? And maybe it is worth prohibiting
this or at least having a WARNING in logs?

Why: I see setups where with growing RAM and shared_buffers set to 25%,
effective_cache_size remains untuned, at some point significantly below the
value of shared_buffers.

On Tue, Nov 6, 2018 at 21:42 Bruce Momjian <bruce(at)momjian(dot)us> wrote:

> On Mon, Nov 5, 2018 at 02:01:12PM -0300, Alvaro Herrera wrote:
> > On 2018-Nov-05, Bruce Momjian wrote:
> >
> > > Well, here are the lines in guc.c:
> > >
> > > gettext_noop("Sets the planner's assumption about the size
> of the data cache."),
> > > gettext_noop("That is, the size of the cache used for
> PostgreSQL data files. "
> > > "This is measured in disk pages, which are
> normally 8 kB each."),
> >
> > I suggest "the size of data caches", plural, in the first line (two
> > letters shorter, since I lost the article). And in the second line, use
> > "... the size of the combined caches used for Pg data files, including
> > both the kernel cache and shared buffers" -- a few words longer, which
> > seems worth it to me.
>
> OK, I handled it slightly differently:
>
>
> https://git.postgresql.org/pg/commitdiff/b43df566b372650a9b9e2a0dd9e695c1f16da14f
>
> I think "the size of" anything plural is confusing so I said "the total
> size of".
>
> --
> Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
> EnterpriseDB http://enterprisedb.com
>
> + As you are, so once was I. As I am, so you will be. +
> + Ancient Roman grave inscription +
>