[rtl] Soft Real Time
I'm involved in a new project where we plan to use dual Power PC Synergy SBCs running Yellow Dog LINUX. Since RT Linux doesn't seem to ready for prime time I have been trying to do deterministic scheduling with the existing system, with some success. So far I: 1.Changed my HZ from 100 to 1000 2.Set the running thread priority to 90 with sched_setscheduler 3.Locked the task in memory with mlockall 4.I used the interval timer, setitimer to do my scheduling I am able to get tasks to down to ~1 ms. And as lone as nothing else is going on it is solid as a rock The problem is that when another process is started, any access to disk, etc I blow my frame, where I get burps out to 10 - 30ms. Is there anything else I might do to make my task more deterministic and is there any hope for RT Linux with Synergy (PPC). Thanks..Al -- [rtl] --- To unsubscribe: echo "unsubscribe rtl" | mail [EMAIL PROTECTED] OR echo "unsubscribe rtl Your_email" | mail [EMAIL PROTECTED] --- For more information on Real-Time Linux see: http://www.rtlinux.org/rtlinux/
Re: [rtl] Soft Real Time
On Sat, 24 Jun 2000, Bernhard Kuhn wrote: [...] A year ago, me and some (former) collegues had the following idea: on an SMP machine, Linux could run in non-SMP-mode on one processor, while RTEMS is using the other processor. Depending on the application, the whole RTEMS-stuff would fit into 512 KByte of memory, an thus fitting completly into the L2-Cache of a Pentium II. Sounds great, for things such as machine control, where you need a known and invarying number of small tasks that just have to run very fast. [...] If there are enough people out there, interessted in that idea, we could revival the project. I'm interested! I guess the same thing would work with ecos too? (http://www.redhat.com/products/ecos/) -- [EMAIL PROTECTED] (Ph.D.)Fax: +32-(0)16-32 29 87 Dept. Mechanical Eng., Div. PMA, Katholieke Universiteit Leuven, Belgium -- [rtl] --- To unsubscribe: echo "unsubscribe rtl" | mail [EMAIL PROTECTED] OR echo "unsubscribe rtl Your_email" | mail [EMAIL PROTECTED] --- For more information on Real-Time Linux see: http://www.rtlinux.org/rtlinux/
Re: [rtl] Soft Real Time
On Sat, 24 Jun 2000, Bernhard Kuhn wrote: Herman Bruyninckx wrote: [ Asymetric Multiprocessing with Linux and another RTOS ] Sounds great, for things such as machine control, where you need a known and invarying number of small tasks that just have to run very fast. That´s not the point! RT-Linux (and RTAI as well) are just fine for this purpose - except the latencies caused by potential cache misses are too big (usualy 5 µs - IMHO, that´s quite ok for advanced machine control, but who knows?). We have a control problem in which we need a simple controller to run at preferably 30 000 Hz... So, keeping everything in cache is really needed... -- [EMAIL PROTECTED] (Ph.D.)Fax: +32-(0)16-32 29 87 Dept. Mechanical Eng., Div. PMA, Katholieke Universiteit Leuven, Belgium -- [rtl] --- To unsubscribe: echo "unsubscribe rtl" | mail [EMAIL PROTECTED] OR echo "unsubscribe rtl Your_email" | mail [EMAIL PROTECTED] --- For more information on Real-Time Linux see: http://www.rtlinux.org/rtlinux/
Re: [rtl] Soft Real Time
Herman Bruyninckx wrote: We have a control problem in which we need a simple controller to run at preferably 30 000 Hz... So, keeping everything in cache is really needed... 30 KHz is ok, as long as some events can be missed or jitters in the range of the period are ok. Otherwise you might run into problems with latencies using Host-to-PCI bridges (but who knows?) ... So, IMHO, it is more wise to design a dedicated controller unit for your application ... Bernhard -- [rtl] --- To unsubscribe: echo "unsubscribe rtl" | mail [EMAIL PROTECTED] OR echo "unsubscribe rtl Your_email" | mail [EMAIL PROTECTED] --- For more information on Real-Time Linux see: http://www.rtlinux.org/rtlinux/
Re: [rtl] Soft Real Time
On Sun, Jun 25, 2000 at 12:04:36AM +0200, Herman Bruyninckx wrote: On Sat, 24 Jun 2000, Bernhard Kuhn wrote: Herman Bruyninckx wrote: [ Asymetric Multiprocessing with Linux and another RTOS ] Sounds great, for things such as machine control, where you need a known and invarying number of small tasks that just have to run very fast. That´s not the point! RT-Linux (and RTAI as well) are just fine for this purpose - except the latencies caused by potential cache misses are too big (usualy 5 µs - IMHO, that´s quite ok for advanced machine control, but who knows?). We have a control problem in which we need a simple controller to run at preferably 30 000 Hz... So, keeping everything in cache is really needed... Do you really need SMP _PowerPC_ ? If not we have something to beta test on SMP x86. -- - Victor Yodaiken FSMLabs: www.fsmlabs.com www.rtlinux.com FSMLabs is a servicemark and a service of VJY Associates L.L.C, New Mexico. -- [rtl] --- To unsubscribe: echo "unsubscribe rtl" | mail [EMAIL PROTECTED] OR echo "unsubscribe rtl Your_email" | mail [EMAIL PROTECTED] --- For more information on Real-Time Linux see: http://www.rtlinux.org/rtlinux/
