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From Philippe Mouawad <philippe.moua...@gmail.com>
Subject Re: Improve our percentiles computation
Date Wed, 15 May 2019 19:56:38 GMT
Hi Felix,

Thanks for your feedback.
Few questions below

On Wed, May 15, 2019 at 9:40 PM Felix Schumacher <
felix.schumacher@internetallee.de> wrote:

>
> Am 15.05.19 um 17:28 schrieb Philippe Mouawad:
> > Hello,
> >
> > I'll start with my team the development of a switch to better percentiles
> > computation which will end as a PR contribution.
> >
> > To recap previous discussions:
> >
> >    - We have currently 2 implementations of Percentiles :
> >       - A custom one used in old listeners
> >       - A new one based on commons-math
> >       - CONS:
> >    - It impacts maintainability as a consequence
> >       - The results are different which confuses users
> >       - Percentiles are not explicitly documented regarding the algorithm
> >       used which also creates confusion :
> >          - https://github.com/apache/jmeter/pull/295
> >          - https://github.com/apache/jmeter/pull/296
> >       - Benefits:
> >       - Have one algorithm in codebase
> >       - Rely on best percentile algo for our use case
> >       - Rely on performing and reliable library HdrHistogram/LatencyUtils
> >       - Improve CO handling
> >    - PREVIOUS ACTIONS:
> >    - It was agreed that switching to HdrHistogram was a good option. This
> >       library is a standard now:
> >          - Used in MicroMeter (used by Spring)
> >          - Used in future JMC
> >
> https://mail.openjdk.java.net/pipermail/jmc-dev/2019-May/000984.html
> >       - Felix started a PR:
> >          - https://github.com/apache/jmeter/pull/380/files
>
> I updated the branch and thus the PR to be hopefully more correct than
> the old one.
>
> I still have a few doubts about the implementation. It seems to me, that
> HdrHistogram is good for collecting the stats, but not optimized for
> asking the stats a lot while the test is running.
>

Which would affect GUI mode testing only right ?
If confirmed we would need to reduce refresh rate ?

>
> That is the reason, that I tried to implement the calculation of some of
> those stats myself. There is a good change, that I completely messed it up.
>
you mean " There is a good chance, that I completely messed it up."

>
> >       - Vladimir mentioned LatencyUtils in this PR:
> >          - Used in MicroMeter
> >          - Based on Gil Tene work who is master of CO related issues as
> >          long as other titles
> >
> >
> > *PROPOSED ACTION PLAN:*
> >
> >    - We'll start our work using LatencyUtils which seems interesting as
> it
> >    provides a PauseDetector which will be useful in our case
> >
> >
> > If you have any note on this, feel free to add your ideas in this thread.
>
> Have a look at the performance of the reports while the stats are
> collected.
>
Thanks

>
> Felix
>
> >
> > Regards
> > Philippe M.
> > UbikLoadPack Team
> >
> >
> >
> >
> >
> >
> > <https://www.openstreetmap.org/#map=18/50.69454/3.16455>
> >
>


-- 
Cordialement.
Philippe Mouawad.

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