Hi Fabien, Sorry for very short report. I feel pgbench is not so complex tool.
Please see below answers to your questions. On Wed, Jun 29, 2016 at 5:07 PM, Fabien COELHO <coe...@cri.ensmp.fr> wrote: > > Hello Sachin, > > Your report is very imprecise so it is hard to tell anything. > > What version of client and server are you running? I am testing it with 9.6-beta1 binaries. For server and client it is same. I am using pgbench on top of postgres_fdw. > On what hardware ? (200 connections => 200 active postgres processes, how > many processes per core are you expecting to run? I am running in small virtual box machine. with 1GB RAM and 2 cores. I think there should not be problem with 200 processes on 2 core machines. I tested same number of concurrent connections on same machine with sysbench it is working fine. I am not sure what is difference between pgbench and sysbench, they might be process based or thread based. But I can say if I can create 200+ concurrent connection with sysbench , i should be able create same with pgbench. Thoughts? > the recommanded value is about 2 connections per physical core...) I think 2 connections per core is very small value . for 200 i need atleast 100 core machine , which is not good. What precise command is started? > How to you know it "comes down to 100 connections"? I put watch on live connections to database. something like : watch -n 1 'ps -ef | grep postgres | grep 192.168.56.101 | wc -l' NOTE: grep cxommand may change as per environment. Also user below query to see active connection. # select count(*) from pg_stat_activity; > Are there error messages from pgbench or postgresql? > > postgresql does not give any error. pgbench says: client 36 aborted in state 2: ERROR: could not connect to server "server_1" DETAIL: FATAL: sorry, too many clients already > My random guess would be that you start too many connections with only one > thread client side and/or on a too small hardware client or server-side for > the expected scale, so given the load and latency some connections just > never get to do anything? > > This may be reason but it should be able to maintain idle connection for that time if never get to do anything. > Maybe try with "-j 20" so that there are not too many connections per > pgbench thread? > > I do not have such good hardware for now. I feel pgbench should be able to perform well on small hardware. Feel free to ask any question regarding setup. > I am testing pgbench with more than 100 connections. also set >> max_connection in postgresql.conf more than 100. >> >> Initially pgbench tries to scale nearby 150 but later it come down to 100 >> connections and stable there. >> >> It this limitation of pgbench? or bug? or i am doing it wrong way? >> >> --- >> I tested it with max_connection = 200 in postgresql.conf >> and pgbench witn -c 180/190/200 >> > > Please reply. >> > > Please send precise information instead of expecting people to guess... > > -- > Fabien > -- Thanks and Regards, Sachin Kotwal
