Re: PATCH: two slab-like memory allocators

On 2017-02-27 07:55:32 -0800, Andres Freund wrote:
> On 2017-02-27 10:32:25 -0500, Tom Lane wrote:
> > Andres Freund <andres(at)anarazel(dot)de> writes:
> > > And pushed slab and its usage. Will have a look at generation.c
> > > tomorrow.
> >
> > Perhaps first you need to find out why so much of the buildfarm
> > is unhappy.
>
> Will do, after a morning coffee.

Hm. Not entirely clear on what's going on yet. I've run the tests on
hydra (community ppc 64 machine), which is pretty similar to termite
which failed [1] with:
TRAP: BadArgument("!(((context) != ((void *)0) && (((((const Node*)((context)))->type) == T_AllocSetContext) || ((((const Node*)((context)))->type) == T_SlabContext))))", File: "/home/pgbuildfarm/buildroot-termite/HEAD/pgsql.build/../pgsql/src/backend/utils/mmgr/mcxt.c", Line: 1010)

The best theory I have so far that I have is that slab.c's idea of
StandardChunkHeader's size doesn't match what mcxt.c think it is
(because slab.c simply embeds StandardChunkHeader, but mcxt uses
MAXALIGN(sizeof(StandardChunkHeader))). That's not good, but I don't
quite see how that'd cause the issue, since StandardChunkHeader's size
should always be properly sized.

Tomas, do you have access to termite (which appears to be run by Craig,
under company mail).

If not, I can push a "blind" fix, but I'd rather have more information.

Greetings,

Andres Freund

[1] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=termite&dt=2017-02-27%2014%3A00%3A06