On Mon, Apr 18, 2016 at 11:24 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Andres Freund <and...@anarazel.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?
I don't recall a specific discussion about it, but the number we would have needed before was gigantic - one per lwlock, which is typically going to be far more than 1024. I mean, at shared_buffers=32MB, there are 4096 buffers using two lwlocks each... never mind everything else that uses lwlocks. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers