Re: pgbench throttling latency limit

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

--
Jan Wieck
Senior Software Engineer
http://slony.info