Re: Estimating HugePages Requirements?

Magnus Hagander <magnus@hagander.net> writes:
> I wonder how hard it would be to for example expose that through a
> commandline switch or tool.

Just try to start the server and see if it complains.
For instance, with shared_buffers=10000000 I get

2021-06-09 15:08:56.821 EDT [1428121] FATAL:  could not map anonymous shared memory: Cannot allocate memory
2021-06-09 15:08:56.821 EDT [1428121] HINT:  This error usually means that PostgreSQL's request for a shared memory
segmentexceeded available memory, swap space, or huge pages. To reduce the request size (currently 83720568832 bytes),
reducePostgreSQL's shared memory usage, perhaps by reducing shared_buffers or max_connections. 

Of course, if it *does* start, you can do the other thing.

Admittedly, we could make that easier somehow; but if it took
25 years for somebody to ask for this, I'm not sure it's
worth creating a feature to make it a shade easier.

            regards, tom lane