Horton

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

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Rowley <dgrowleyml@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Julien Rouhaud <rjuju123@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Yura Sokolov <y.sokolov@postgrespro.ru>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2022-09-20T01:23:08Z
Lists: pgsql-hackers 
David Rowley <dgrowleyml@gmail.com> writes:
> Aside from that, I don't have any ideas on how to get rid of the
> possible additional datumCopy() from non-Var arguments to these window
> functions.  Should we just suffer it? It's quite likely that most
> arguments to these functions are plain Vars anyway.

No, we shouldn't.  I'm pretty sure that we have various window
functions that are deliberately designed to take advantage of the
no-copy behavior, and that they have taken a significant speed
hit from your having disabled that optimization.  I don't say
that this is enough to justify reverting the chunk header changes
altogether ... but I'm completely not satisfied with the current
situation in HEAD.

			regards, tom lane

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