On 5/1/13 4:57 AM, Fabien COELHO wrote:
The use case of the option is to be able to generate a continuous gentle load for functional tests, eg in a practice session with students or for testing features on a laptop.
If you add this to https://commitfest.postgresql.org/action/commitfest_view?id=18 I'll review it next month. I have a lot of use cases for a pgbench that doesn't just run at 100% all the time. I had tried to simulate something with simple sleep calls, but I realized it was going to take a stronger math basis to do the job well.
The situations where I expect this to be useful all require collecting latency data and then both plotting it and doing some statistical analysis. pgbench-tools computes worst-case and 90th percentile latency for example, along with the graph over time. There's a useful concept that some of the official TPC tests have: how high can you get the throughput while still keeping the latency within certain parameters. Right now we have no way to simulate that. What we see with write-heavy pgbench is that latency goes crazy (>60 second commits sometimes) if all you do is hit the server with maximum throughput. That's interesting, but it's not necessarily relevant in many cases.
-- Greg Smith 2ndQuadrant US g...@2ndquadrant.com Baltimore, MD PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
