Horton

Re: Change GUC hashtable to use simplehash?

Jeff Davis <pgsql@j-davis.com>

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From: Jeff Davis <pgsql@j-davis.com>
To: John Naylor <johncnaylorls@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Tom Lane <tgl@sss.pgh.pa.us>, Gurjeet Singh <gurjeet@singh.im>, pgsql-hackers@postgresql.org
Date: 2023-12-08T20:34:59Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Silence warning in older versions of Valgrind

  2. Revert "Speed up tail processing when hashing aligned C strings, take two"

  3. Speed up tail processing when hashing aligned C strings, take two

  4. Teach fasthash_accum to use platform endianness for bytewise loads

  5. Add macro to disable address safety instrumentation

  6. Convert uses of hash_string_pointer to fasthash equivalent

  7. Speed up tail processing when hashing aligned C strings

  8. Add helper functions for dshash tables with string keys.

  9. Fix warnings in cpluspluscheck

  10. Further cosmetic review of hashfn_unstable.h

  11. Simplify initialization of incremental hash state

  12. Add optimized C string hashing

  13. Add inline incremental hash functions for in-memory use

  14. Make all Perl warnings fatal

I committed 867dd2dc87, which means my use case for a fast GUC hash
table (quickly setting proconfigs) is now solved.

Andres mentioned that it could still be useful to reduce overhead in a
few other places:

https://postgr.es/m/20231117220830.t6sb7di6h6am4ep5@awork3.anarazel.de

How should we evaluate GUC hash table performance optimizations? Just
microbenchmarks, or are there end-to-end tests where the costs are
showing up?

(As I said in another email, I think the hash function APIs justify
themselves regardless of improvements to the GUC hash table.)

On Wed, 2023-12-06 at 07:39 +0700, John Naylor wrote:
> > There's already a patch to use simplehash, and the API is a bit
> > cleaner, and there's a minor performance improvement. It seems
> > fairly
> > non-controversial -- should I just proceed with that patch?
> 
> I won't object if you want to commit that piece now, but I hesitate
> to
> call it a performance improvement on its own.
> 
> - The runtime measurements I saw reported were well within the noise
> level.
> - The memory usage starts out better, but with more entries is worse.

I suppose I'll wait until there's a reason to commit it, then.

Regards,
	Jeff Davis