print results with percentile

[WANG Hui]

Hello Aleksey,



I fire up the discussion again on the percentile-based latency measurement because I really like this tool and want use it for all my performance measurement.



Currently, the mode provided by JMH to measure the latency is the SampleTime mode. It's documented as follows :



Runs by continuously calling Benchmark methods, and randomly samples the time needed for the call.

This mode automatically adjusts the sampling frequency, but may omit some pauses which missed the sampling measurement.

This mode is time-based, and it will run until the iteration time expires.



Is the latency recorded for each method invocation ?

How does automatic freq selection work ?

Would it be possible for the max latency to be omitted?



Regarding the overheads of timestamping infrastructure, IMHO, as long as we want to observe a system, we must inject some facility to feel the system.

Therefore, the overhead is not avoidable but it should be fine if the cost is not comparable with the under-observation system.

What are your opinions on the histogram tool which should be rather modest in terms of overhead ?



Thanks a lot,

Hui



-----Original Message-----
From: Aleksey Shipilev [mailto:aleksey.shipilev at oracle.com]
Sent: vendredi 4 septembre 2015 10:51
To: WANG Hui; jmh-dev at openjdk.java.net
Subject: Re: print results with percentile



On 09/04/2015 11:48 AM, WANG Hui wrote:

> What are reasons that JMH is not enabling percentile by default ?  Is

> it due to the overhead of recording percentiles ?



Yes, due to the overheads of timestamping infrastructure. JMH is very widely used in doing throughput nanobenchmarks, where the infra costs should be at absolute minimum.



Thanks,

-Aleksey


*******************************

This e-mail contains information for the intended recipient only. It may contain proprietary material or confidential information. If you are not the intended recipient you are not authorised to distribute, copy or use this e-mail or any attachment to it. Murex cannot guarantee that it is virus free and accepts no responsibility for any loss or damage arising from its use. If you have received this e-mail in error please notify immediately the sender and delete the original email received, any attachments and all copies from your system.