On 2/13/2013 6:08 AM, Michael Haberler wrote: > Am 13.02.2013 um 11:37 schrieb andy pugh: > >> On 13 February 2013 10:15, Michael Haberler <mai...@mah.priv.at> wrote: >> >>> http://www.xenomai.org/pipermail/xenomai/2013-February/027675.html >> This sounds familiar, there is a similar situation with RTAI: >> http://wiki.linuxcnc.org/cgi-bin/wiki.pl?RealTime >> and the "cpu hog" near the bottom. > Mick just observed that the "nohlt idle=poll" boot option does in fact > improve latency figures significantly > > It might well be the case that the same option does have an impact with RTAI, > too > > It's worth a try - I just dont have 'laggy' hardware at my hands here > > - Michael > >> After a bit more searching, I guess you are aware of that as exactly >> the same name for it is being used on the Xenomai page. >> >> -- >> atp >>
As I've been telling Michael in a side channel, my latency test results from late last fall with an AMD Athlon II X4-640 cpu on a ASUS M488T-M motherboard do not show the same behavior being reported for this newer AMD cpu and <whatever> motherboard. Back then, I ran Michael's x686 xenomai kernel with a variety of configurations - various cpus isolated or not, various combinations of servo and base threads on different cpus, various combinations of cpu-hog runs. (see https://sites.google.com/site/manisbutareed/linuxcnc-2-5/xenomai-user-threads) Latencies were always within a factor of 2x to 4x of my best RTAI numbers for the same hardware. The only latency buster I encountered was peeking at the xenomai stats. Executing "cat /proc/xenomai/stat" would reliably blow up the base thread in particular (jumps 250us or more). I am overwhelmed by my home healthcare-provider chores and have not been able to catch up to the latest "wisdom" and repeat my testing accordingly. I do have one new data point that didn't cost me a lot of time to generate: I rebooted the same system with the additional kernel boot parameters "nohlt idle=poll" A quick 'n dirty latency-test showed similar jitter to what I had seen before. Maybe they are a tad better, but I have no time now to be quantitative. For the record, "cat /proc/xenomai/stat" still blows up the latency numbers. Regards, Kent ------------------------------------------------------------------------------ Free Next-Gen Firewall Hardware Offer Buy your Sophos next-gen firewall before the end March 2013 and get the hardware for free! Learn more. http://p.sf.net/sfu/sophos-d2d-feb _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
