Horton

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

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Tomas Vondra <tomas.vondra@enterprisedb.com>, Amit Kapila <amit.kapila16@gmail.com>, Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, Yura Sokolov <y.sokolov@postgrespro.ru>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2022-09-02T08:11:12Z
Lists: pgsql-hackers

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On Thu, 1 Sept 2022 at 12:46, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> David Rowley <dgrowleyml@gmail.com> writes:
> > Maybe we should just consider always making room for a sentinel for
> > chunks that are on dedicated blocks. At most that's an extra 8 bytes
> > in some allocation that's either over 1024 or 8192 (depending on
> > maxBlockSize).
>
> Agreed, if we're not doing that already then we should.

Here's a patch to that effect.

I've made it so that there's always space for the sentinel for all
generation.c and slab.c allocations. There is no power of 2 rounding
with those, so no concern about doubling the memory for power-of-2
sized allocations.

With aset.c, I'm only adding sentinel space when size >
allocChunkLimit, aka external chunks.

David

Commits

  1. Harden memory context allocators against bogus chunk pointers.

  2. Improve our ability to detect bogus pointers passed to pfree et al.

  3. Remove MemoryContextContains().

  4. Remove uses of MemoryContextContains in nodeAgg.c and nodeWindowAgg.c.

  5. Temporarily make MemoryContextContains return false

  6. Make MemoryContextContains work correctly again

  7. Make more effort to put a sentinel at the end of allocated memory

  8. Fix some possibly latent bugs in slab.c

  9. Various cleanups of the new memory context header code

  10. Revert "Add missing padding from MemoryChunk struct"

  11. Use MAXALIGN() in calculations using sizeof(SlabBlock)

  12. Add missing padding from MemoryChunk struct

  13. Improve performance of and reduce overheads of memory management