From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4E70E940.5010500@domain.hid> Date: Wed, 14 Sep 2011 19:49:52 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <4E70A876.3020009@domain.hid> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-help] multicore: reserving core(s) for Xenomai List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jeff Weber Cc: xenomai@xenomai.org On 09/14/2011 05:00 PM, Jeff Weber wrote: > On Wed, Sep 14, 2011 at 8:13 AM, Gilles Chanteperdrix < > gilles.chanteperdrix@xenomai.org> wrote: > >> On 09/14/2011 02:18 PM, Henri Roosen wrote: >> [snip] >>> >>> What I would like to do is to run the Xenomai realtime threads on one >>> core of the multi-core CPU. And I would like to reserve this core only >>> for the Xenomai realtime threads. >>> >> [snip] >> The kernel has an "isolcpus" option, which allows to specify which cpus >> should not be used by Linux. >> >> See Documentation/kernel-parameters.txt in the linux kernel sources for >> an explanation. >> >> > I tried to do this a year ago with the kernel isolcpus option, but could not > get this to work: > >> Gilles Chanteperdrix to Jeff, xenomai-help >> Jeff wrote: >>> What is the best method for segregating Xenomai and Linux by CPU? I was >>> unable to do this cleanly using /proc/xenomai/affinity for Xenomai, >>> together with the Linux isolcpus boot option. Details below. >> >> I have no definite answer, I have not checked. What I suspect, however, >> is that when you try and force an affinity for a Xenomai thread, it >> tries and apply this affinity in secondary mode, i.e. as a plain Linux >> thread. So, will fail if the target thread is not in the "isolcpus" >> mask. In other words, a Xenomai thread can not run on a CPU where Linux >> threads can not run. This explanation sounds like crap: looking at the documentation, it seems that when using the "isolcpus" option, threads can run on an isolated cpu if they force their affinity. -- Gilles.