Eyal Wilde <eyal@xxxxxxxxxxxxxxxx> wrote: > now, i run a test that simulates 20 simultaneous clients, asking > for "account-id" randomly. once a client get a result, it > immediately asks for another one. the test last 5 seconds. i use > a connection pool (with Tomcat web-server). the pool is > automatically increased to ~20 connections (as expected). the > result is postgresql dose ~60 "account-id"s, whereas ms-sql dose > ~330 "account-id"s. postgresql shows that each "account-id" took > about 400-1000 msec ,which is so much slower than the ~60 msec of > a single execution. > the hardware is one 4-core xeon. 8GB of ram. the database size is > just a few GB's. centos-6.2. > > do you think the fact that postgresql use a process per connection > (instead of multi-threading) is inherently a weakness of > postgrsql, regarding scale-up? I doubt that has much to do with anything. > would it be better to limit the number of connections to something > like 4, so that executions don't interrupt each other? The point where a lot of workloads hit optimal performance is with the number of active connections limited to ((core count * 2) + effective spindle count). Determining "active spindle count can be tricky (for example it is zero in a fully-cached read-only workload), so it takes more information than you've given us to know exactly where the optimal point might be, but if it's a single drive, then if you have 4 cores (not 2 cores with hyperthreading) you might want to limit your connection pool to somewhere in the 8 to 10 range. You generally should configure a connection pool to be transaction based, with a request to start a transaction while all connections are busy causing the request queue, with completion of a transaction causing it to pull a request for the queue, if available. I'm pretty sure that Tomcat's pool supports this. Could you describe your disk system and show us the result of running the query?: http://wiki.postgresql.org/wiki/Server_Configuration -Kevin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
