Re: Spinlocks and semaphores in 9.2 and 9.3

Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2016-04-18 11:07:08 -0400, Tom Lane wrote:
>> Did you want to actually review this patch, or should I just push it?

> No, I'm good, you should push it. I did a quick scan of the patch, and
> it looks sane. For a second I was concerned that there might be a
> situation in which this patch increases the total number of semaphore
> needed, which might make backpatching a bit problematic - but it appears
> that that'd be a very absurd configuration.

I was actually wondering whether it'd make sense to cut the number of
underlying semaphores to 128 or 512 or thereabouts. But I think we had
that discussion when the daa7527afc227443 patch went in to begin with,
and convinced ourselves that 1024 was okay. Robert, do you recall the
reasoning?

(The thing that gave me pause about this was noticing that I could not
start two such postmasters concurrently on my RHEL6 box, without changing
the default system limits on number of SysV semaphores.)

regards, tom lane