Re: Estimating HugePages Requirements?

On 8/9/21, 8:43 PM, "Andres Freund"  wrote:
> I don't like putting this into PostmasterMain(). Either BootstrapMain()
> (specifically checker mode) or GucInfoMain() seem like better places.

I think BootstrapModeMain() makes the most sense.  It fits in nicely
with the --check logic that's already there.  With v3, the following
command can be used to retrieve the amount of shared memory required.

        postgres --output-shmem -D dir

While testing this new option, I noticed that you can achieve similar
results today with the following command, although this one will
actually try to create the shared memory, too.

        postgres --check -D dir -c log_min_messages=debug3 2> >(grep IpcMemoryCreate)

IMO the new option is still handy, but I can see the argument that it
might not be necessary.

> That seems like an ugly API to me. Why don't we split the size
> determination and shmem creation functions into two?

I did it this way in v3.

Nathan