Durumdara <durumdara@xxxxxxxxx> writes: > But the number of threads option (j I think) confused me. At first I > thought the total connection number is simply the multiplication of c and j > (subconnections). > As I saw this is untrue. > So I don't know how this utility works really in the background. There are -j threads in the pgbench process, and -c connections to the server (hence -c backend processes on the server side). Each of the pgbench threads is responsible for sending queries to a subset of the connections. Setting -j more than -c is useless (I forget if it's actually an error). If you set -j to, say, half of -c then each thread has exactly two connections to manage. If -j is too small compared to -c then pgbench itself tends to become the bottleneck. regards, tom lane
