On Mon, Apr 18, 2016 at 11:53 AM, Robert Haas <robertmh...@gmail.com> wrote: > 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:
Oops, hit send too soon. http://docstore.mik.ua/manuals/hp-ux/en/B2355-60130/semmni.5.html That's from 2007 and indicates a default maximum of 2048. So it would be fairly easy to hit the limit. -- 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