From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <55117766.4090003@web.de> Date: Tue, 24 Mar 2015 15:40:38 +0100 From: Jan Kiszka MIME-Version: 1.0 References: In-Reply-To: Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: quoted-printable Subject: Re: [Xenomai] xenomia on virtual box List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: r t , xenomai@xenomai.org On 2015-03-24 12:54, r t wrote: > Hi, > = > perhaps a silly question but we are trying to get our pre- xenomai patched > kernel to run on VirtualBox. Playing about a bit. Well we already have it > running that is not the problem. > = > The question is whether there is any chance that we will get good (or any) > latency/ realtime performance if the kernel was compiled on another machi= ne > other than the host environment currently hosting the VirtualBox? > = > Instructions to achieve what we are playing with explicitly state that the > kernel must be compiled on the host then installed on the guest which lea= ds > to believe (as I would intuitively expect) that it is not possible to > abstract a xenomai environement from the hardware. However to my surprize > the xenomai patched kernel does noet seeem to have to run on the host. H= ow > does xenomai on the guest machine achieve good realtime performance if the > host is still free to act as it wishes in terms of accessing hardware? > = > = > Can anyone perhaps shed some light on this? Virtualization, specifically if VirtualBox-based, destroys real-time for a Xenomai guest system. You can use such setups very well for functional tests provided they do not fail due to longer delays or high jitters. VirtualBox has a fairly poor interface for Linux guests /wrt virtual clocks and their calibration. Therefore, we frequently run into issues when setting up Xenomai tests on Windows hosts. The best real-time environment you can get right now out of a common hypervisor is stacking KVM on top of PREEMPT-RT. But that alone will not suffice, you will also have to tune the guest to avoid priority inversions in the hypervisor's machine emulation. Jan -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 181 bytes Desc: OpenPGP digital signature URL: