Ulrich Schwab wrote: > I think that CONFIG_PREEMPT should reduce the jitter of Your measurement, > most > importantly the worst case switch time, for wich You need a long test run > under heavy load. > CONFIG_PREEMPT is there to provide more determinism, which usually has a > price > in performance. > Realtime is about determinism not performance (or speed). > Its not maximum speed but guaranteed minimum speed.
You are absolutely right. I put my system under some load (dd) and made two tests. One was with CONFIG_PREEMPT and one without. The worst case switch time jitter was about 30% lower in the CONFIG_PREEMPT case, so your prediction was right. > Since the probability of a preemption during the mode switch without > CONFIG_PREEMPT is lower, it might take a long time until the worst case mode > switch time is observed. Sorry but I don't understand what you are meaning. Let me explain my point of view. When a realtime task in the Xenomai-Domain makes a linux-systemcall the task is migrated fully automatically to the Linux-Domain as soon as we reach the next preemption point in the Linux-Kernel. Due to the fact that preemptability of the linux-kernel increase when using CONFIG_PREEMPT, the time to the next preemption point should decrease, right? I don't get the point of your last sentence. Thanks for help, Markus Franke -- Nichts ist so praktisch wie eine gute Theorie!
begin:vcard fn:Markus Franke n:Franke;Markus adr;quoted-printable:;;Vettersstra=C3=9Fe 64/722;Chemnitz;Saxony;09126;Germany email;internet:[EMAIL PROTECTED] x-mozilla-html:FALSE url:http://www.tu-chemnitz.de/~franm version:2.1 end:vcard
_______________________________________________ Xenomai-help mailing list [email protected] https://mail.gna.org/listinfo/xenomai-help
