Re: [PATCH] pgbench --throttle (submission 7 - with lag measurement)

Greg Smith wrote:

Thanks. I didn't look at the code, but while trying to read the docs:

> + <para>
> + High rate limit schedule lag values, that is values not small with
> + respect to the actual transaction latency, indicate that something is
> + amiss in the throttling process.

I couldn't really parse the above. Of the first six words, which one is
a verb? Is there a noun that needs to be plural? Is there a word that
shouldn't be there?

... Oh, I think it makes sense if I assume that "rate limit schedule lag"
is a single concept .. but if so, that phrase seems too many words for it.
(So when the RLSL values are high, this indicates a problem. Is that
what the above means?)

Also, it took me a while to understand what "values not small" means. I
think there must be a way to phrase this that's easier to understand.

> High lag can highlight a subtle
> + problem there even if the target rate limit is met in the end. One
> + possible cause of schedule lage is insufficient pgbench threads to
> + handle all of the clients.

typo "lage" above.

> To improve that, consider reducing the
> + number of clients, increasing the number of threads in pgbench, or
> + running pgbench on a separate host. Another possibility is that the
> + database is not keeping up with the load at some point. When that
> + happens, you will have to reduce the expected transaction rate to
> + lower schedule lag.
> + </para>

Thanks

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Álvaro Herrera http://www.2ndQuadrant.com/
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