From: Philippe Gerum <rpm@xenomai.org>
To: Jan Kiszka <jan.kiszka@domain.hid>
Cc: xenomai@xenomai.org, Rudolf Marek <rudolf.marek@domain.hid>
Subject: Re: [Xenomai-help] negative values of latency/klatency
Date: Tue, 28 Feb 2006 13:52:11 +0100 [thread overview]
Message-ID: <4404477B.2040102@domain.hid> (raw)
In-Reply-To: <440442FC.8090100@domain.hid>
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.
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 12:52 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 [this message]
2006-02-28 13:02 ` Philippe Gerum
2006-02-28 14:13 ` [Xenomai-core] " Jan Kiszka
2006-02-28 15:22 ` Philippe Gerum
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