I have a read-only database that I am testing the performance of to get a sense of how many concurrent users I can support. The database fits entirely in RAM so I expect there to be little to no disk activity. Because of this, I expect throughput to scale almost linearly with the number of CPUs I have. However, that is not what I am seeing. For example, take the following results. Postgres 8.3.8 Fedora 9 Intel(R) Xeon(R) CPU 5160 @ 3.00GHz X 2 (4 cores total) 4 GB RAM -bash-3.2$ pgbench -c 1 -S -t 400000 test starting vacuum...end. transaction type: SELECT only scaling factor: 64 number of clients: 1 number of transactions per client: 400000 number of transactions actually processed: 400000/400000 tps = 11373.127109 (including connections establishing) tps = 11373.907131 (excluding connections establishing) -bash-3.2$ pgbench -c 2 -S -t 200000 test starting vacuum...end. transaction type: SELECT only scaling factor: 64 number of clients: 2 number of transactions per client: 200000 number of transactions actually processed: 400000/400000 tps = 11422.541958 (including connections establishing) tps = 11423.979642 (excluding connections establishing) -bash-3.2$ pgbench -c 3 -S -t 200000 test starting vacuum...end. transaction type: SELECT only scaling factor: 64 number of clients: 3 number of transactions per client: 200000 number of transactions actually processed: 600000/600000 tps = 11330.641664 (including connections establishing) tps = 11332.074176 (excluding connections establishing) -bash-3.2$ pgbench -c 4 -S -t 100000 test starting vacuum...end. transaction type: SELECT only scaling factor: 64 number of clients: 4 number of transactions per client: 100000 number of transactions actually processed: 400000/400000 tps = 11747.647262 (including connections establishing) tps = 11750.710786 (excluding connections establishing) During these tests top(1) reported 60-70% idle CPU. As you see, the TPS remains the same as I increase the number of clients. These results make it look like PostgreSQL is single-threaded and not taking advantage of the multiple cores. Could someone please explain? -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
