| From: | Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> |
|---|---|
| To: | tomas(dot)vondra(at)enterprisedb(dot)com |
| Cc: | nathandbossart(at)gmail(dot)com, tgl(at)sss(dot)pgh(dot)pa(dot)us, reid(dot)thompson(at)crunchydata(dot)com, pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: Oversight in slab.c SlabContextCreate(), initial memory allocation size is not populated to context->mem_allocated |
| Date: | 2022-08-01 07:57:44 |
| Message-ID: | 20220801.165744.517561753479500363.horikyota.ntt@gmail.com |
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| Lists: | pgsql-hackers |
At Fri, 29 Jul 2022 21:16:51 +0200, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> wrote in
> I don't think this can make meaningful difference - as you mention, we
> only really use this to decide when to spill to disk etc. So maybe
> you'll spill a bit sooner, but the work_mem is pretty crude threshold
> anyway, people don't tune it to an exact byte value (which would be
> pretty futile anyway).
From another perspective.. SlabStats includes the header size into
its total size. So it reports a different total size from
MemoryContextMemAllocated() (For example, 594 bytes vs 0). Since this
is an inconsistency within slab.c, no users will notice that
difference in the field.
> OTOH it does seem like an oversight, or at least an inconsistency with
> the two other contexts, so if anyone feels like tweaking it ...
regards.
--
Kyotaro Horiguchi
NTT Open Source Software Center
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