bug#68244: hash-table improvements

[Eli Zaretskii]

> From: Mattias Engdegård <mattias.engdegard@gmail.com>
> Date: Thu, 4 Jan 2024 17:27:53 +0100
> 
> It's the hash-table's turn to be subjected to some performance tuning. The 
> implementation has changed very little over the years and it's not so much a 
> matter of a single big thing to fix as many small ones, so the list of 
> changes is fairly long but ever little helps.
> 
> A working patch series can be found in the scratch/hash-table-perf branch. 
> Although it should all be satisfactory and an improvement on what was before, 
> there are a couple of details that I'd like to do better, which is why this 
> hasn't been merged yet: the way shared hash_table_test structs are cached 
> isn't very elegant, nor is the way we deal with Qunbound in pdumper.c.

Thanks.  Any data about the actual performance gains?

Adding Stefan to the discussion, in case he has comments and
suggestions.