More is better?
Not always. I did some more tests, and confirmed that this particular workload actually gets slower as you add more than 2 cores.
sysbench --num-threads=${i} --test=oltp --pgsql-user=bench --pgsql-db=bench --db-driver=pgsql --max-time=60 --max-requests=0 --oltp-read-only=on run
Here’s the results, with the tests run on absolutely identical hardware. (HP DL360, 2.00 GHz E5335 Xeon, 10K RPM SAS drives, 10 GB of RAM)
I know 6.2 isn’t the greatest for SMP, but I was still surprised to learn that we could get significantly lower overall performance by adding more processors.
I tried to test 7.0, but the 7.0 installer didn’t seem to recognize the iLO virtual keyboard tonight. Maybe tomorrow will go better.