Re: pgbench throttling latency limit

On 2015-10-20 20:55:46 +0200, Andres Freund wrote:
> On 2014-08-14 15:01:53 +0200, Fabien COELHO wrote:
> > 
> > Add --limit to limit latency under throttling
> > 
> > Under throttling, transactions are scheduled for execution at certain times.
> > Transactions may be far behind schedule and the system may catch up with the
> > load later. This option allows to change this behavior by skipping
> > transactions which are too far behind schedule, and count those as skipped.
> > 
> > The idea is to help simulate a latency-constrained environment such as a
> > database used by a web server.
> 
> I was just trying to run tests with this, but as far as I can see it
> doesn't really work:
> 
> pgbench postgres -M prepared -c 72 -j 72 -P 5 -T 3600 -R40000 -L100

> progress: 365.0 s, 18392.1 tps, lat 94.857 ms stddev 23.917, lag 90.980 ms, 106244 skipped
> 
> 100k skipped transactions at a rate limit of 40k? That doesn't seem right.

Argh. It's just because I used -P5. It's a bit confusing that the other
options are per second, and this is per interval...

Andres