On Sat, Nov 3, 2012 at 6:53 PM, Jeff Janes <jeff.janes@xxxxxxxxx> wrote: > On Wed, Oct 31, 2012 at 11:39 AM, Merlin Moncure <mmoncure@xxxxxxxxx> wrote: >> On Tue, Oct 30, 2012 at 4:58 PM, Jeff Janes <jeff.janes@xxxxxxxxx> wrote: >>> On Mon, Oct 29, 2012 at 5:11 PM, Catalin Iacob <iacobcatalin@xxxxxxxxx> wrote: >>> >>>> pgbouncer 1.4.2 installed from Ubuntu's packages on the same machine >>>> as Postgres. Django connects via TCP/IP to pgbouncer (it does one >>>> connection and one transaction per request) and pgbouncer keeps >>>> connections open to Postgres via Unix socket. >>> >>> Isn't pgbouncer single-threaded? >>> >>> If you hitting it with tiny queries as fast as possible from 20 >>> connections, I would think that it would become the bottleneck. >> >> Single threaded asynchronous servers are known to scale better for >> this type of workload than multi-threaded systems because you don't >> have to do locking and context switching. > > How much locking would there be in what pgbouncer does? > > On a 4 CPU machine, if I run pgbench -c10 -j10 with dummy queries > (like "select 1;" or "set timezone...") against 2 instances of > pgbouncer, I get nearly twice the throughput as if I use only one > instance. > > A rather odd workload, maybe, but it does seem to be similar to the > one that started this thread. > > >> pgbouncer is an absolute marvel and should be standard kit in any case >> you're concerned about server scaling in terms of number of active >> connections to the database. I'm in the camp that application side >> connection pools are junk and should be avoided when possible. > > I have nothing against pgbouncer, but it is not without consequences. agreed -- also, I was curious and independently verified you results. pgbouncer doesn't lock -- if you strace it, it just goes epoll_wait, recv_from, send_to endlessly while under heavy load from pgbench. This suggests that the bottleneck *is* pgbouncer, at least in some cases. It's hard to believe all the userland copying is causing that, but I guess that must be the case. merlin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
