Am 21.11.2012 um 06:42 schrieb Anders Wallin: > On 11/20/2012 8:47 AM, Michael Haberler wrote: >>> I just verified this combination works, for the standard Raspberry >>> Raspbian kernel 3.2.27+ with Posix threads (aka 'simulator'), and >>> with Xenomai 3.2.21 for somewhat better performance >> >> Very cool! >> >> What sort of latency numbers are you seeing with Xenomai? >> > > over on the forum there is this link > http://linuxcnc.mah.priv.at/rpi/rpi-rtperf.html
Errata: I mentioned in this article the default Raspbian kernel is an rt-preempt-patched kernel - it is not; I got confused with all those PREEMPT tags. I still have to find a kernel for the Raspberry which has RT_PREEMPT patches applied. Also, I now have some more clue as to the reasons of some of the delays; I'll update the paper. --- Those who are stubbornly determined at software stepping with ARM's (or potentially other architectures) and userland threads should have a look at how Sergej did this in miniemc2 - it is interesting insofar as I would call it 'minimally kernel-invasive' (the rest of it is all userland, and still getting good performance): overview: http://code.google.com/p/miniemc2/wiki/miniEMC2_internals userland part: http://code.google.com/p/miniemc2/source/browse/trunk/emc2-arm/src/hal/components/miniemcdrv.c kernel part: http://code.google.com/p/miniemc2/source/browse/trunk/modules/modminiemc/modminiemc.c NB: the latter module is is very hardware dependent at the lowest level - it requires a free hardware timer and a free ARM 'fast interrupt' both of which might not be available on a given platform, like the Raspberry (on which I think both of the two prerequisites are already occupied). -m > > the educated guess on IRC yesterday was that the Pi might be able to run > linuxcnc motion with a 1ms servo-thread and a lightweight GUI. Software > step-generation is probably too demanding. > > I'd like to run these latency-tests myself when I get my hands on a Pi. > Preferably with hardware in the loop, i.e. actually output pulses at 1ms > and use external hardware to check that the 1ms timing is OK. > > AW > ------------------------------------------------------------------------------ > Monitor your physical, virtual and cloud infrastructure from a single > web console. Get in-depth insight into apps, servers, databases, vmware, > SAP, cloud infrastructure, etc. Download 30-day Free Trial. > Pricing starts from $795 for 25 servers or applications! > http://p.sf.net/sfu/zoho_dev2dev_nov > _______________________________________________ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers ------------------------------------------------------------------------------ Monitor your physical, virtual and cloud infrastructure from a single web console. Get in-depth insight into apps, servers, databases, vmware, SAP, cloud infrastructure, etc. Download 30-day Free Trial. Pricing starts from $795 for 25 servers or applications! http://p.sf.net/sfu/zoho_dev2dev_nov _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
