Re: Add bump memory context type and use it for tuplesorts

On Tue, 16 Apr 2024 at 17:13, Amul Sul <sulamul(at)gmail(dot)com> wrote:
> Attached is a small patch adding the missing BumpContext description to the
> README.

Thanks for noticing and working on the patch.

There were a few things that were not quite accurate or are misleading:

1.

> +These three memory contexts aim to free memory back to the operating system

That's not true for bump. It's the worst of the 4. Worse than aset.
It only returns memory when the context is reset/deleted.

2.

"These memory contexts were initially developed for ReorderBuffer, but
may be useful elsewhere as long as the allocation patterns match."

The above isn't true for bump. It was written for tuplesort. I think
we can just remove that part now. Slab and generation are both old
enough not to care why they were conceived.

Also since adding bump, I think the choice of which memory context to
use is about 33% harder than it used to be when there were only 3
context types. I think this warrants giving more detail on what these
3 special-purpose memory allocators are good for. I've added more
details in the attached patch. This includes more details about
freeing malloc'd blocks

I've tried to detail out enough of the specialities of the context
type without going into extensive detail. My hope is that there will
be enough detail for someone to choose the most suitable looking one
and head over to the corresponding .c file to find out more.

Is that about the right level of detail?

David