From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4FC6698E.2090800@xenomai.org> Date: Wed, 30 May 2012 20:40:14 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <4FC637EB.90908@xenomai.org> <4FC63C53.3020805@xenomai.org> <20120530155743.GK32727@csclub.uwaterloo.ca> <4FC6506C.9090609@xenomai.org> <20120530175754.GL32727@csclub.uwaterloo.ca> In-Reply-To: <20120530175754.GL32727@csclub.uwaterloo.ca> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] a question about ADEOS List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Lennart Sorensen Cc: xenomai@xenomai.org On 05/30/2012 07:57 PM, Lennart Sorensen wrote: > On Wed, May 30, 2012 at 06:53:00PM +0200, Gilles Chanteperdrix wrote: >> You can see for yourself with the xenomai-forge branch. It is already in >> a usable state. I do not buy the scheduler argument: the linux scheduler >> does pretty much the same separation between real-time and non real-time >> tasks as the separation which happens with xenomai. And the scheduler >> for real-time tasks is simple, it does not need to know much more than >> the tasks priorities, I do not see what more you would like to control. > > I have been looking at it a bit. Maybe I should give it a try soon. > > Based on what I have seen for the real time linux patches, you can set > priorities of kernel threads as well, which would be nice at times. I am not sure to get what you mean, Xenomai kernel threads priority are configurable as well. > > Perhaps our use is just not normal, in that we ahve an application that > uses realtime, but has some work to do that is very low priority (and > not in need of realtime) but needs to share memory space and resources > with the stuff that does have to be real time, which makes it hard to > make linux tasks run before the less important stuff in the xenomai > application runs. It works using an idle priority thread, but it would > be nice to have better control of it, which I hope the rt patches for > linux would allow. Maybe I am hoping for too much. Starting with Xenomai 2.6, if you create a xenomai thread with scheduling policy SCHED_OTHER (and priority 0), it returns to secondary mode as soon as possible, so, is handled by Linux scheduler as a low priority thread most of the time. If this task is cpu bound, you probably can even decrease its time slices by using the renice() service. -- Gilles.