On 03/22/2016 10:44 AM, Fabien COELHO wrote:

1) regular-latency.png

I'm wondering whether it would be clearer if the percentiles
where relative to the largest sample, not to itself, so that the
figures from the largest one would still be between 0 and 1, but
the other (unpatched) one would go between 0 and 0.85, that is
would be cut short proportionnaly to the actual performance.

I'm not sure what you mean by 'relative to largest sample'?

You took 5% of the tx on two 12 hours runs, totaling say 85M tx on
one and 100M tx on the other, so you get 4.25M tx from the first and
5M from the second.


I'm saying that the percentile should be computed on the largest one
(5M), so that you get a curve like the following, with both curve
having the same transaction density on the y axis, so the second one
does not go up to the top, reflecting that in this case less
transactions where processed.

Huh, that seems weird. That's not how percentiles or CDFs work, and I don't quite understand what would that tell us.


Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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