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

From: David Rowley <dgrowleyml(at)gmail(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Andres Freund <andres(at)anarazel(dot)de>, 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: 2022-08-09 23:17:38
Message-ID: CAApHDvq=4t4sEGL119fC4A=AUsQE6_y2CBd9_5cV_itLEe+pdA@mail.gmail.com
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Thanks for giving this a look.

On Wed, 10 Aug 2022 at 02:37, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> # We also add a restriction that block sizes for all 3 of the memory
> # allocators cannot be 1GB or larger. We would be unable to store the
> # number of bytes that the block is offset from the chunk stored beyond this
> #1GB boundary on any block that was larger than 1GB.
>
> Earlier in the commit message, you say that allocations of 1GB or more
> are stored in dedicated blocks. But here you say that blocks can't be
> more than 1GB. Those statements seem to contradict each other. I guess
> you mean block sizes for blocks that contain chunks, or something like
> that?

I'll update that so it's more clear.

But, just to clarify here first, the 1GB restriction is just in
regards to the maxBlockSize parameter when creating a context.
Anything over set->allocChunkLimit goes on a dedicated block and there
is no 1GB size restriction on those dedicated blocks.

David

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