From: Philippe Gerum <rpm@xenomai.org>
To: Philippe Gerum <rpm@xenomai.org>
Cc: xenomai@xenomai.org, Rudolf Marek <rudolf.marek@domain.hid>,
Jan Kiszka <jan.kiszka@domain.hid>
Subject: Re: [Xenomai-help] negative values of latency/klatency
Date: Tue, 28 Feb 2006 14:02:23 +0100 [thread overview]
Message-ID: <440449DF.7060109@domain.hid> (raw)
In-Reply-To: <4404477B.2040102@domain.hid>
Philippe Gerum wrote:
> Jan Kiszka wrote:
>
>> Rudolf Marek wrote:
>>
>>> Hello all,
>>>
>>> I tried the latency and klatency demo on some PPC procesor(s) (e500
>>> and 60x) and the measurement results are rather strange.
>>> I observed this with arbitrary version of Adeos/ipipe and on Xenomai
>>> 2.0.3 older 2.0.x too.
>>>
>>> -sh-3.00# ./run -- -T 10 -h -l 5
>>> ...
>>> RTT| 00:00:01
>>> RTH|----klat min|----klat avg|----klat max| overrun|---klat
>>> best|--klat worst
>>> RTD| -4525| -4323| 5777| 0|
>>> -4525| 5777
>>> RTD| -4525| -4444| -1777| 0|
>>> -4525| 5777
>>> RTD| -4525| -4444| -565| 0|
>>> -4525| 5777
>>> RTD| -4525| -4444| -1656| 0|
>>> -4525| 5777
>>> RTD| -4525| -4444| -1979| 0|
>>> -4525| 5777
>>> RTT| 00:00:06
>>> RTH|----klat min|----klat avg|----klat max| overrun|---klat
>>> best|--klat worst
>>> RTD| -4525| -4444| -2020| 0|
>>> -4525| 5777
>>> RTD| -4525| -4444| -1050| 0|
>>> -4525| 5777
>>> RTD| -4525| -4444| -1616| 0|
>>> -4525| 5777
>>> RTD| -4525| -4444| -1898| 0|
>>> -4525| 5777
>>> RTD| -4525| -4444| -1939| 0|
>>> -4525| 5777
>>> ...
>>> Well if I set scheduling latency from automatic "0" to "1" I get:
>>
>>
>>
>> 0 means automatic latency compensation (which does not seem to work that
>> well here, it overcompensates),
>
>
> Dynamic determination of the intrinsic latency during nucleus startup
> has been dropped some time ago (circa fusion 0.6.8), because it just did
> not provide accurate results. Since then, when 0 is specified in
> Kconfig, the value read from include/asm-*/calibration.h is substituted.
> In this case, 9500 ns are taken for a ppc32 platform, which is likely
> too high for this board. Setting ~4500 in Kconfig would better
> approximate the latency.
>
Btw, the following would work too in order to easily test various settings
dynamically:
$ echo 4500 > /proc/xenomai/latency
> while 1 effectively means "no
>
>> hardware/software scheduling latency" (=> 1 ns). See also help of the
>> related kernel configuration parameters.
>>
>>
>>> -sh-3.00# ./run -- -T 10 -h -l 5
>>>
>>> RTT| 00:00:01
>>> RTH|----klat min|----klat avg|----klat max| overrun|---klat
>>> best|--klat worst
>>> RTD| 4767| 4929| 15191| 0|
>>> 4767| 15191
>>> RTD| 4767| 4808| 8282| 0|
>>> 4767| 15191
>>> RTD| 4767| 4808| 8080| 0|
>>> 4767| 15191
>>> RTD| 4808| 4808| 7838| 0|
>>> 4767| 15191
>>> RTD| 4767| 4808| 7272| 0|
>>> 4767| 15191
>>> RTT| 00:00:06
>>> RTH|----klat min|----klat avg|----klat max| overrun|---klat
>>> best|--klat worst
>>> RTD| 4808| 4808| 7555| 0|
>>> 4767| 15191
>>> RTD| 4767| 4808| 7959| 0|
>>> 4767| 15191
>>> RTD| 4767| 4808| 7393| 0|
>>> 4767| 15191
>>> RTD| 4808| 4808| 7191| 0|
>>> 4767| 15191
>>> RTD| 4767| 4808| 7313| 0|
>>> 4767| 15191
>>>
>>> Is this a bug or feature please? Can someone throw the light?
>>> Good would be to print the units to the numbers too (ns).
>>>
>>
>>
>> That was likely a layout question of the latency tool's output. We could
>> simply dump something like "All latencies in nanoseconds" during
>> start-up. Would this be more helpful?
>>
>> Jan
>>
>>
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> Xenomai-help mailing list
>> Xenomai-help@domain.hid
>> https://mail.gna.org/listinfo/xenomai-help
>
>
>
--
Philippe.
next prev parent reply other threads:[~2006-02-28 13:02 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-27 16:12 [Xenomai-help] negative values of latency/klatency Rudolf Marek
2006-02-28 12:33 ` Jan Kiszka
2006-02-28 12:52 ` Philippe Gerum
2006-02-28 13:02 ` Philippe Gerum [this message]
2006-02-28 14:13 ` [Xenomai-core] " Jan Kiszka
2006-02-28 15:22 ` Philippe Gerum
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=440449DF.7060109@domain.hid \
--to=rpm@xenomai.org \
--cc=jan.kiszka@domain.hid \
--cc=rudolf.marek@domain.hid \
--cc=xenomai@xenomai.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.