Re: max_connections limit

Sean Chittenden <sean(at)chittenden(dot)org> writes:
> I wonder how correct the following is:

> SHMMAXPGS = ((max_connections * shared_buffers * 16K) + (wal_buffers *
> 8K) + (max_fsm_relations * 40B) + (max_fsm_pages * 6B)) /
> page_size

Not very. shared_buffers are 8K apiece, not 16K, and you don't multiply
them by max_connections. There *is* a multiplier for max_connections
but I'm not sure what it is --- less than 1K, probably. Also you should
allow for the lock table, which will be some small multiplier times
max_connections * max_locks_per_transaction.

> SEMMNI = 2 * max_connections (????)
> SEMMSL = SEMMNI
> SHMSEG = 10 # (???? this is a per SysV process setting)
> SEMMNS = 1.5 * max_connections (????)
> SEMMNU = 0.75 * max_connections (????)
> SEMUME = 10 (????)

Dunno where you got these semaphore numbers from, either.

regards, tom lane