On Oct 9, 2012, at 3:24 AM, Tomas Vondra <tv@xxxxxxxx> wrote: > On 9.10.2012 00:33, Evgeny Shishkin wrote: >>> >>> pgbench: Old server >>> >>> pgbench -i -s 100 -U test >>> pgbench -U test -c ... -t ... >>> >>> -c -t TPS >>> 5 20000 3777 >>> 10 10000 2622 >>> 20 5000 3759 >>> 30 3333 5712 >>> 40 2500 5953 >>> 50 2000 6141 >>> >>> New server >>> -c -t TPS >>> 5 20000 2733 >>> 10 10000 2783 >>> 20 5000 3241 >>> 30 3333 2987 >>> 40 2500 2739 >>> 50 2000 2119 >> >> On new server postgresql do not scale at all. Looks like contention. > > Why? The evidence we've seen so far IMHO suggests a poorly performing > I/O subsystem. Post a few lines of "vmstat 1" / "iostat -x -k 1" > collected when the pgbench is running, that might tell us more. > Because 50 clients can push io even with small read ahead. And hear we see nice parabola. Just guessing anyway. > Try a few very basic I/O tests that are easy to understand rather than > running bonnie++ which is quite complex. For example try this: > > time sh -c "dd if=/dev/zero of=myfile.tmp bs=8192 count=4194304 && sync" > > dd if=myfile.tmp of=/dev/null bs=8192 > > The former measures sequential write speed, the latter measures > sequential read speed in a very primitive way. Watch vmstat/iostat and > don't bother running pgbench until you get a reasonable performance on > both systems. > > > Tomas > > > -- > Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-performance -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
