On 2014-04-28 13:32:45 +0300, Heikki Linnakangas wrote: > On 04/28/2014 12:39 PM, Andres Freund wrote: > >On 2014-04-28 10:48:30 +0300, Heikki Linnakangas wrote: > >>On 04/26/2014 09:27 PM, Andres Freund wrote: > >>>I don't think we need to decide this without benchmarks proving the > >>>benefits. I basically want to know whether somebody has an actual > >>>usecase - even if I really, really, can't think of one - of setting > >>>max_connections even remotely that high. If there's something > >>>fundamental out there that'd make changing the limit impossible, doing > >>>benchmarks wouldn't be worthwile. > >> > >>It doesn't seem unreasonable to have a database with tens of thousands of > >>connections. Sure, performance will suffer, but if the connections sit idle > >>most of the time so that the total load is low, who cares. Sure, you could > >>use a connection pooler, but it's even better if you don't have to. > > > >65k connections will be absolutely *disastrous* for performance because > >of the big PGPROC et al. > > Well, often that's still good enough.
That may be true for 2-4k max_connections, but >65k? That won't even *run*, not to speak of doing something, in most environments because of the number of processes required. Even making only 20k connections will probably crash your computer. > >The main reason I want to shrink it is that I want to make pin/unpin > >buffer lockless and all solutions I can come up with for that require > >flags to be in the same uint32 as the refcount. For performance > >it'd be beneficial if usagecount also fits in there. > > Would it be enough to put only some of the flags in the same uint32? It's probably possible, but would make things more complicated. For a "feature" nobody is ever going to use. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers