From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <5626198.1178177559304.JavaMail.ngmail@domain.hid> Date: Thu, 3 May 2007 09:32:39 +0200 (CEST) From: "M. Koehrer" In-Reply-To: <46360605.4020901@domain.hid> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable References: <46360605.4020901@domain.hid> <17043901.1177943488672.JavaMail.ngmail@domain.hid> Subject: Re: [Xenomai-help] [RTnet-users] Xenomai/rtnet vs. 2.6.21 realtime preempt patch List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: jan.kiszka@domain.hid, mathias_koehrer@domain.hid Cc: xenomai@xenomai.org, rtnet-users@domain.hid Hi Jan, > > I have tried the latest 2.6.21 kernel + Ingo Molnar's realtime preempt > patch > > (see: http://rt.wiki.kernel.org/index.php/RT_PREEMPT_HOWTO) > >=20 > > And I am really amazed about the results. > > On my Pentium 4D (dual core) system, 3.2 GHz, I ran the cyclictest > > application (which is something similar to the "latency" application of > Xenomai/RTAI) > > and I get values below 15 microseconds on my PC (for a single task runn= ing > with 200 microseconds). > >=20 .... > >=20 > > Currently, my application is working quite nice using Xenomai/rtnet > however there are some > > drawbacks like the issue with limited IRQs: Sharing of IRQs between > Ethernet-Drivers of rtnet > > and non-realtime drivers is not possible (at least I did not manage > that...). > > A smooth usage of real time features from a "standard" kernel could hel= p > here! >=20 > Nope, not really. As I think to have explained earlier, IRQ sharing > between drivers that are designed for real-time and others that are not > will never work deterministically. That has nothing to do with the > design of your RTOS underneath. Actually, the same issue once came up > for -rt over some ARM board that did poor IRQ line sharing as well. >=20 > Jan I agree, the best is actually to have separate IRQs for real time and non r= eal time drivers. However, reality shows me, that this is very hard to get with standard PCs. I can plug in one or two PCI boards to have an unique IRQ for them. However= , if I want to use more PCI boards IRQ sharing cannot be avoided. As with the preempt patch, the duration of non-realtime IRQ routines seems = to be fairly short. >>From this, I think it is at least an option to share IRQs between real time= and non real time drivers even if the IRQ routine of the non real time driver may lead to a delay of = the real time IRQ routine. It is a question of acceptable delays for the IRQs. Regards Mathias --=20 Mathias Koehrer mathias_koehrer@domain.hid Viel oder wenig? Schnell oder langsam? Unbegrenzt surfen + telefonieren ohne Zeit- und Volumenbegrenzung? DAS TOP ANGEBOT JETZT bei Arcor: g=FCnsti= g und schnell mit DSL - das All-Inclusive-Paket f=FCr clevere Doppel-Sparer, nur 39,85 =80 inkl. DSL- und ISDN-Grundgeb=FChr! http://www.arcor.de/rd/emf-dsl-2