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
