Re: scalability bottlenecks with (many) partitions (and more)

On 3/3/25 19:10, Andres Freund wrote:
> Hi,
>
> On 2024-09-21 20:33:49 +0200, Tomas Vondra wrote:
>> I've finally pushed this, after many rounds of careful testing to ensure
>> no regressions, and polishing.
>
> One minor nit: I don't like that FP_LOCK_SLOTS_PER_BACKEND is now non-constant
> while looking like a constant:
>
> #define FP_LOCK_SLOTS_PER_BACKEND (FP_LOCK_SLOTS_PER_GROUP * FastPathLockGroupsPerBackend)
>
> I don't think it's a good idea to have non-function-like #defines that
> reference variables that can change from run to run.
>

Fair point, although it can't change "run to run" - not without a
restart. It's not a proper constant, of course, but it seemed close
enough. Yes, it might confuse people into thinking it's a constant, or
is there some additional impact?

The one fix I can think of is making it look more like a function,
possibly just like this:

#define FastPathLockSlotsPerBackend() \
(FP_LOCK_SLOTS_PER_GROUP * FastPathLockGroupsPerBackend)

Or do you have another suggestion?

regards

--
Tomas Vondra