From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 3 Jun 2009 11:17:05 +0200 (CEST) From: Adrien LECOINTRE Message-ID: <103585745.148571244020625685.JavaMail.root@domain.hid> In-Reply-To: <2060886493.147971244020544226.JavaMail.root@domain.hid> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-help] How to chose between xenomai and preempt RT List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: xenomai@xenomai.org Jeff Angielski wrote: > Of course, just by choosing to use Xenomai, you don't get hard realtime. > You still need to design your system and software correctly. Yes but a software can be well designed on PREEMPT_RT as well. I built a kernel and a filesystem with the less possible number of driver. After startup there is only an ATA driver and bash running on my system! In this situation I really doubt that a big latency can occurs. Then if my real-time software uses a specific device I just have to write my own driver (instead of using a "basic" linux driver) if I want to know exactly what's going on my system and keep a hard real-time behavior. Those are basics things that we always do when designing a real-time software on any RT OS. Of course for a real-time software with a lot of non-real-time loads it's probably easier to use Xenomai and let Linux deals with loads. I read a lot of things about PREEMPT_RT not providing hard real-time but I coudn't find any test case which shows that. My loads are probably not good enough but it shouldn't be so difficult to find a way to cause a significant latency on a supposed non-hard-real-time OS. Adrien.