- ISTM that there "thread start time" should be initialized at the
    beginning of threadRun instead of in the loop *before* thread creation,
    otherwise the thread creation delays are incorporated in the
    performance measure, but ISTM that the point of pgbench is not to
    measure thread creation performance...

I noticed that, but it seemed a pretty minor issue.

Not for me, because the "max lag" measured in my first version was really the threads creation time, not very interesting.

Did you look at the giant latency spikes at the end of the test run I submitted the graph for?

I've looked at the graph you sent. I must admit that I did not understand exactly what is measured and where it is measured. Because of its position at the end of the run, I thought of some disconnection related effects when pgbench run is interrupted by a time out signal, so some things are done more slowly. Fine with me, we are stopping anyway, and out of the steady state.

I wanted to nail down what was causing those before worrying about the startup timing.

Well, the short answer is that I'm not worried by that, for the reason explained above. I would be worried if it was anywhere else but where the transactions are interrupted, the connections are closed and the threads are stopped. I may be wrong:-)


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