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 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@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ As you are, so once was I. As I am, so you will be. +
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