Re: Reducing the chunk header sizes on all memory context types

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: David Rowley <dgrowleyml(at)gmail(dot)com>
Cc: Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Robert Haas <robertmhaas(at)gmail(dot)com>, Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Reducing the chunk header sizes on all memory context types
Date: 2022-08-29 15:25:57
Message-ID: 3207033.1661786757@sss.pgh.pa.us
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I wrote:
> So the bug is in fact in David's changes, and it consists in palloc
> sometimes handing back non-maxaligned pointers. I find it mildly
> astonishing that we managed to get through core regression tests
> without such a fault surfacing, but there you have it.

Oh! I just noticed that the troublesome context (rb->change_context)
is a SlabContext, so it may be that this only happens in non-aset
contexts. It's a lot easier to believe that the core tests never
exercise the case of pfree'ing a slab chunk.

regards, tom lane

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