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From: Piotr Gregor <pgregor@quadrant-systems.co.uk>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	"rolf.freitag@email.de" <rolf.freitag@email.de>
Cc: r t <linux-rt-users@vger.kernel.org>
Subject: RE: Variance, Standard Deviation, Skewness and Kurtosis for cyclictest results?
Date: Mon, 26 Jun 2017 15:59:20 +0000	[thread overview]
Message-ID: <AM3PR02MB1305D909595CD5A0AE25D29C1DF0@AM3PR02MB130.eurprd02.prod.outlook.com> (raw)
In-Reply-To: <20170626143035.kir3ym6so6yifrza@linutronix.de>

Hi Sebastian,

I think Rolf understands that but he is simply interested in deviation anyway.
I can agree deviation gives some more insight into nature of latency observed even if it is clear
then max peak is what determines real-timeness of the setup. One may be interested in distribution
of latency - you may have two setups with same average and max peak while there is much less
meaningful peaks on one than on the other.

cheers,
Piotr

-----Original Message-----
From: linux-rt-users-owner@vger.kernel.org [mailto:linux-rt-users-owner@vger.kernel.org] On Behalf Of Sebastian Andrzej Siewior
Sent: 26 June 2017 15:31
To: rolf.freitag@email.de
Cc: r t <linux-rt-users@vger.kernel.org>
Subject: Re: Variance, Standard Deviation, Skewness and Kurtosis for cyclictest results?

On 2017-06-24 00:38:49 [+0200], rolf.freitag@email.de wrote:
> Hi,
Hi,

> many programs, e. g. ping also print the standard deviation of the measured times, so i would like get the standard deviation(s) also from cyclictest.
> It's easy to also calculate Variance, Skewness and Kurtosis in the 
> same pass: https://www.johndcook.com/blog/skewness_kurtosis/
> Has someone planned to implement this in cyclictest?

cyclictest prints min/avg/max. min and avg are nice to look at. The important part is the max value. If you have avg at 30us and max at 500us then you know, that you can't meet your deadline for a cycle of 400us.

> Regards,
> 
> Rolf

Sebastian
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  reply	other threads:[~2017-06-26 15:59 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-23 22:38 Variance, Standard Deviation, Skewness and Kurtosis for cyclictest results? rolf.freitag
2017-06-26 14:30 ` Sebastian Andrzej Siewior
2017-06-26 15:59   ` Piotr Gregor [this message]
2017-06-26 16:20     ` Sebastian Andrzej Siewior
2017-06-26 17:12     ` rolf.freitag
2017-06-27  8:18     ` Nicholas Mc Guire
2017-06-27 10:33       ` Piotr Gregor
2017-06-27 11:39         ` Nicholas Mc Guire
2017-06-27 12:33           ` Piotr Gregor

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