Re: [HACKERS] Re: Max backend limits cleaned up

Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> writes:
> I am getting:
> IpcSemaphoreCreate: semget failed (No space left on device) key=5432017,
> num=16, permission=600
> [ later ]
> I got it working by adding a -N 32 to the postmaster startup. Looks
> like my site BSD/OS can't start 64 backends. Some of my configuration
> is wrong. Perhaps we need 32 as the default.

Yeah, I was thinking about that myself. I left the default -N setting
at 64 on the theory that people who had gone to the trouble of making
sure they had proper kernel configurations should not get surprised by
v6.5 suddenly reducing the default number-of-backends limit.

On the other hand, we have reason to believe that a lot of systems are
not configured to allow Postgres to grab 64 semaphores, so if we don't
reduce the default -N value we will almost certainly see a lot of gripes
just like the above when people move to 6.5. (I think -N 32 would work
as a default on minimally-configured systems, but cannot prove it.)

I haven't got a real strong feeling either way. Opinions?

regards, tom lane