From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, Petr Jelinek <petr(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, John Gorman <johngorman2(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: PATCH: two slab-like memory allocators |
Date: | 2017-02-27 17:42:01 |
Message-ID: | 20170227174201.yrofai7neyp6shb2@alap3.anarazel.de |
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Lists: | pgsql-hackers |
On 2017-02-27 12:27:48 -0500, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > 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.
>
> Uh, wrong. On a 32-bit machine with debug enabled, StandardChunkHeader
> will contain 3 4-byte fields. However, there are some such machines on
> which MAXALIGN is 8. For example, looking at termite's configure
> output:
>
> checking size of void *... 4
> checking size of size_t... 4
> checking size of long... 4
> checking alignment of short... 2
> checking alignment of int... 4
> checking alignment of long... 4
> checking alignment of long long int... 8
> checking alignment of double... 8
>
> axolotl's output looks similar. I expect my old HPPA dinosaur
> will show the failure as well.
Yea, I hadn't yet realized when writing that that termite actually,
despite running on ppc64, compiles a 32bit postgres. Will thus
duplicate StandardChunkHeader's contents in to slab.c :( - I don't see
an easy way around that...
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