RE: Using PGTune - is it a good source for system configuration?

Yes, I have found that most PostgreSQL workloads do benefit some (like 25% to 30%) from Intel hyperthreading.

With 4 threads, I would probably start out at:

max_worker_processes = 4
max_parallel_workers_per_gather = 2
max_parallel_workers = 3
max_parallel_maintenance_workers = 1

And then keep an eye on htop ... and go from there. Remember that for this generation of processor, the speculative execution patches make context switching (changing which software thread a hyperthread is working on) quite expensive, so its bad to max out the processor, and your gains above the 2 cores will be small.

But honestly I have never run PostgreSQL on a machine with fewer than 12 cores / 24 threads.

--Stephen

-----Original Message-----
From: Pól Ua Laoínecháin <linehanp(at)tcd(dot)ie>
Sent: Wednesday, September 1, 2021 12:16
Cc: pgsql-novice <pgsql-novice(at)lists(dot)postgresql(dot)org>
Subject: Re: Using PGTune - is it a good source for system configuration?

Hi, and thanks for replying.

> Not according to its "about" page...

Yeah, sure, it's not a silver bullet, but the thrust of my question
was: do the community experts consider it reliable enough as a first approximation?

Your remarks about "better than the generic defaults" reassures me that this is the case.

This is just my laptop - but I've taken PGTune's recommendations before for a data loading and it was a real help...

One other question that I forgot to include in my original!

I have a two CPU core (that's why I put 2 for the number of CPUs) but my processor supports hyperthreading (Intel Core i5, 7th Gen), so should I really put 4 as the no.

Changing this from 2 to 4 changes the

work_mem from 41943kB to 20971kB and the worker settings from

max_worker_processes = 2
max_parallel_workers_per_gather = 1
max_parallel_workers = 2
max_parallel_maintenance_workers = 1

to

max_worker_processes = 4
max_parallel_workers_per_gather = 2
max_parallel_workers = 4
max_parallel_maintenance_workers = 2

So, which would be the correct Number of CPUs setting given my processor?

TIA and rgs,

Pól...

> David J.