From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4667DA1F.4010907@domain.hid> Date: Thu, 07 Jun 2007 12:12:47 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <7289437c0706060801i299d6881w31cc5ffee3444ace@domain.hid> <1181143109.17978.101.camel@domain.hid> <7289437c0706062254v2a386894oeb498459877d5086@domain.hid> <4667AA4D.6070505@domain.hid> <7289437c0706070042gf4346ddj1c4ee3ac20a068d2@domain.hid> <4667BBBE.1040405@domain.hid> <4667CEF2.2050509@domain.hid> <4667D008.80109@domain.hid> <4667D167.9030001@domain.hid> <4667D2CC.2060006@domain.hid> In-Reply-To: <4667D2CC.2060006@domain.hid> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-help] Cyclictest List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: xenomai-help Jan Kiszka wrote: > Gilles Chanteperdrix wrote: > >>Jan Kiszka wrote: >> >>>Gilles Chanteperdrix wrote: >>> >>> >>>>Jan Kiszka wrote: >>>> >>>> >>>>>Perrine Martignoni wrote: >>>>> >>>>> >>>>> >>>>>>Ok. I'll do this. >>>>>> >>>>>>But I don't understand why the same application compiled without any links >>>>>>with Xenomai give different results if there is Xenomai in the kernel. >>>>> >>>>>[Looking at your numbers again] Hmm, maybe some rounding issue of ticks >>>>>due to whatever side-effect of I-pipe. We would first of all need the >>>>>usual set of information (.config, involved versions) and also >>>>>/sys/devices/system/clocksource/clocksource0/current_clocksource. >>>> >>>>Maybe what Perrine is observing is simply the overhead of the I-pipe ? >>>>I mean, Linux is Xenomai idle task, so it is acceptable for Linux >>>>numbers to be a bit worse than when Xenomai is not running. >>> >>>I bit worse is expected. But I think we are seeing 1 or 2 ticks wake-up >>>delays here. As far as I understood, they are not due to Xenomai >>>consuming significant cycles in the background, are they, Perrine? >> >>What I see is latencies 5us longer. 5us on ARM is almost nothing, keep >>in mind that a simple syscall on ARM already takes 10 us. >> > > > T: 0 ( 732) P:99 I: 10500 C: 2291 Min: 41 Act: 2281 Avg: 5075 Max: 10224 > > vs. > > T: 0 ( 893) P:99 I: 10000 C: 1756 Min: 13407 Act: 13536 Avg: 13452 Max: 13693 > > Thus the _minimum_ and the _average_ wakeup time of a Linux task > increase fairly significant here. That's the point. Given a reasonable > runtime of both test, this /could/ be considered as a regression of a > Xenomai-enabled Linux kernel. Ok, results are in milliseconds, not microseconds. I guess what we observe here is an effect of Xenomai timer interception. Perrine, what version of the I-pipe patch are you using ? -- Gilles Chanteperdrix