From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <440449DF.7060109@domain.hid> Date: Tue, 28 Feb 2006 14:02:23 +0100 From: Philippe Gerum MIME-Version: 1.0 Subject: Re: [Xenomai-help] negative values of latency/klatency References: <440324EE.6030309@domain.hid> <440442FC.8090100@domain.hid> <4404477B.2040102@domain.hid> In-Reply-To: <4404477B.2040102@domain.hid> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philippe Gerum Cc: xenomai@xenomai.org, Rudolf Marek , Jan Kiszka 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.