From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <440FE276.2080609@domain.hid> Date: Thu, 09 Mar 2006 10:08:22 +0200 From: Heikki Lindholm MIME-Version: 1.0 Subject: Re: [Xenomai-help] Xenomai vs. RTLinux References: <440F5F23.7000703@domain.hid> <440F7B35.1050107@domain.hid> In-Reply-To: <440F7B35.1050107@domain.hid> Content-Type: text/plain; charset=ISO-8859-15; 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: Jan Kiszka Cc: xenomai@xenomai.org Jan Kiszka kirjoitti: > Jeff Webb wrote: > >>Xenomai developers and users, >> >>Our company is looking at the possibility of porting our >>hardware-in-the-loop (HWIL) simulations from RTLinuxFree to a new >>real-time operating system. We are currently considering Xenomai and >>RTLinuxPro as possible options. I am personally biased towards free >>software, but our customers do not necessarily share this bias. I am >>attempting to put together a presentation comparing the advantages and >>disadvantages of the two systems as they would be used in our HWIL >>simulations. Any comments you have would be appreciated. >> >>We are currently using RTLinuxFree-3.2-pre3 running on Fedora Core 1 >>(2.4.22 linux kernel) for our in-house HWIL simulations on rack-mounted >>x86 PC hardware. We have been satisfied with the functionality of >>RTLinuxFree over the past few years, although we have been disappointed >>by the lack of maintenance and development that has occurred since the >>primary developers focused their efforts on developing RTLinuxPro. >>Because there is no RTLinuxFree release that supports the 2.6 kernel, > > > Well, I'm not following this in every details, but there is something > now for RTLinux/GPL (the independent community RTLinux). Anyway, the > maintenance situation is not significantly better there - too few users, > too few developers. I did some investigation of these things last year and at least then only thing available for linux 2.6 was a patch from fsmlabs, which (1) didn't work, (2) nobody maintained, (3) nobody cared about, (4) was x86 only. The word from rtlinux/gpl folk was that they're probably going to use some more generic virtualizer- type-of-thing for 2.6 support instead of porting the existing rtlinux 2.4 stuff over. >>I wrote some simple test programs to compare the scheduling jitter and >>interrupt latency for RTLinuxFree, Xenomai-kernel-space, and >>Xenomai-user-space applications. My tests are not rigorous by any >>means, but it seems that the worst-case measurements are pretty >>similar. Xenomai *may* be slightly better from the limited data I have >>taken. Does anyone care to share their own observations? > > > Would surprises me. From what I know of RTLinux/GPL (RTAI is similar > here, BTW), the critical paths are involving less code than Xenomai. > That's due to the different IRQ redirection layers, the nucleus > abstraction of Xenomai, maybe also to some yet missing optimisations. > Anyway, Xenomai is favouring flexibility and maintainability here over > the last microsecond. But if the target platform is something beginning with x86_64, few instructions here and there probably won't matter.. -- Heikki Lindholm