Re: Estimating HugePages Requirements?

On 9/20/21, 7:29 PM, "Michael Paquier" <michael@paquier.xyz> wrote:
> On Tue, Sep 21, 2021 at 12:08:22AM +0000, Bossart, Nathan wrote:
>> Should we also initialize the shared memory GUCs in bootstrap and
>> single-user mode?  I think I missed this in bd17880.
>
> Why would we need that for the bootstrap mode?
>
> While looking at the patch for shared_memory_size, I have looked at
> those code paths to note that some of the runtime GUCs would be set
> thanks to the load of the control file, but supporting this case
> sounded rather limited to me for --single when it came to shared
> memory and huge page estimation and we don't load
> shared_preload_libraries in this context either, which could lead to
> wrong estimations.  Anyway, I am not going to fight hard if people
> would like that for the --single mode, even if it may lead to an
> underestimation of the shmem allocated.

I was looking at this from the standpoint of keeping the startup steps
consistent between the modes.  Looking again, I can't think of
a strong reason to add it to bootstrap mode.  I think the case for
adding it to single-user mode is a bit stronger, as commands like
"SHOW shared_memory_size;" currently return 0.  I lean in favor of
adding it for single-user mode, but it's probably fine either way.

Nathan