Hello everyone I wite because I have a great problem and I have no idea how resolve this: This is the situation: I have installed a postgresql server 9.6.2 on Ubuntu server 16.04.2 LTS with this specifications: 12 cores y 30 GB de RAM. I have created a database with pgbench for testing and the performance are very bad with synchronous commit. These are the results: scaling factor: 1 query mode: simple number of clients: 50 number of threads: 12 duration: 30 s number of transactions actually processed: 2773 latency average = 544.336 ms latency stddev = 617.941 ms tps = 91.180927 (including connections establishing) tps = 91.194080 (excluding connections establishing) By analyzing the postgres log with pgbadger I could see that the updates take a long time for a table with 10 tuples only. Then I ran a explain analyze and the explain results contradict what the test throws: Update on pgbench_tellers (cost=4.14..8.16 rows=1 width=358) (actual time=0.021..0.021 rows=0 loops=1) -> Bitmap Heap Scan on pgbench_tellers (cost=4.14..8.16 rows=1 width=358) (actual time=0.010..0.010 rows=1 loops=1) Recheck Cond: (tid = 5) Heap Blocks: exact=1 -> Bitmap Index Scan on pgbench_tellers_pkey (cost=0.00..4.14 rows=1 width=0) (actual time=0.005..0.005 rows=1 loops=1) Index Cond: (tid = 5) Planning time: 0.052 ms Execution time: 0.043 ms I have runned the same test in other machines with less RAM and CPU and the results are always better than this: Any help to identify the problem could be very appreciated. Regards |
