On Mon, Apr 18, 2016 at 11:34 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Andres Freund <and...@anarazel.de> writes: >> On 2016-04-18 11:24:07 -0400, Tom Lane wrote: >>> (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.) > >> Hm, is that different before/after the patch? Because afaics at around >> NBuffers = 1000, the number of semaphores should be lower after the >> patch? > > Yeah, that was probably the argument we used before. But it's true that a > postmaster built with --disable-spinlocks is harder to test than one built > without (because you're going from ~100 semas to ~1100 semas, at default > configuration). If we believe that the main real use-case for this switch > is testing, that's not a very nice property. > > The bottom line IMO is that --disable-spinlocks is actually not that awful > for low-stress, low-concurrency scenarios; for example, it doesn't change > the runtime of make installcheck-parallel very much for me. On the other > hand, for high-concurrency scenarios you'd darn well better get a real > spinlock implementation. Given that sort of scope of use, it seems like > a hundred or so underlying semas should be plenty, and it'd be less likely > to cause operational problems than 1024.
I suppose that's probably true. I thought surely any system worth its salt wouldn't have a problem with 1024 semaphores, but a quick Google search for "hp-ux semmns" turned up this page: -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers