On 09/05/2014 10:12 AM, Fabien COELHO wrote:
Note that despite pg appaling latency performance, in may stay well over
the 90% limit, or even 100%: when things are going well a lot of
transaction run in about ms, while when things are going bad transactions
would take a long time (although possibly under or about 1s anyway), *but*
very few transactions are passed, the throughput is very small. The fact
that during 15 seconds only 30 transactions are processed is a detail that
does not show up in the metric.

I haven't used the real pgbench for a long time. I will have to look at your patch and see what the current version actually does or does not.

What I have been using is a Python version of pgbench that I wrote for myself when I started learning that language. That one does record both values, the DB transaction latency and the client response time (time from the request being entered into the Queue until transaction commit). When I look at those results it is possible to have an utterly failing run, with <60% of client response times being within 2 seconds, but all the DB transactions are still in milliseconds.

As said, I'll have to take a look at it. Since I am on vacation next week, getting ready for my first day at EnterpriseDB, this may actually happen.


Jan Wieck
Senior Software Engineer

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