|From:||Yugo NAGATA <nagata(at)sraoss(dot)co(dot)jp>|
|To:||Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>|
|Cc:||Asif Rehman <asifr(dot)rehman(at)gmail(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>|
|Subject:||Re: Fix around conn_duration in pgbench|
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Thank you for looking at it.
On Tue, 27 Jul 2021 03:04:35 +0900
Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote:
> case CSTATE_FINISHED:
> + /* per-thread last disconnection time is not measured */
> Could you tell me why we don't need to do this measurement?
We don't need to do it because it is already done in CSTATE_END_TX state when
the transaction successfully finished. Also, we don't need it when the thread
is aborted (that it, in CSTATE_ABORTED case) because we can't report complete
results anyway in such cases.
I updated the comment.
> - /* no connection delay to record */
> - thread->conn_duration = 0;
> + /* connection delay is measured globally between the barriers */
> This comment is really correct? I was thinking that the measurement is not necessary here because this is the case where -C option is not specified.
This comment means that, when -C is not specified, the connection delay is
measured between the barrier point where the benchmark starts
/* READY */
and the barrier point where all the thread finish making initial connections.
/* GO */
> start = pg_time_now();
> disconnect_all(state, nstate);
> thread->conn_duration += pg_time_now() - start;
> We should measure the disconnection time here only when -C option specified (i.e., is_connect variable is true)? Though, I'm not sure how much this change is helpful to reduce the performance overhead....
You are right. We are measuring the disconnection time only when -C option is
specified, but it is already done at the end of transaction (i.e., CSTATE_END_TX).
We need disconnection here only when we get an error.
Therefore, we don't need the measurement here.
I attached the updated patch.
Yugo NAGATA <nagata(at)sraoss(dot)co(dot)jp>
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