Hi,
[EMAIL PROTECTED] wrote:
>
> On Thu, Mar 23, 2000 at 03:06:27PM +0000, Stuart Hughes wrote:
> > [EMAIL PROTECTED] wrote:
> > >
> > >
> > > I'm thinking of adding RT schedulable Linux processes that run solely in user
> > > space -- when they do a syscall they fall out of RT scheduling.
> > > They would be memory protected and able to access standard libraries: they
> > > would really only be useful for high precision compute tasks and should connect
> > > to RT via fifos. Is there much interest in such a feature?
> > >
> >
> > Yes, and if you do, you'll have to call it LXRT, as hard real-time in
> > user space in RTAI exits *now* in the current release (1.2)
>
> The LXRT approach seems very useful for teaching purposes, but
> if I understand it correctly does not do what I have in mind or match
> the RTLinux model very well. Perhaps I misunderstand it.
You do. What I answered before to your challange in user space, i.e.:
> "Nice challange. I took it, in a slightly different way, as follows:
>
> ping - f server
> do make -j 4 bzImage
> while "true"; do ls -aR /; done
> while "true"; do cat /proc/interrupts; done
>
> while running 3 hard real time tasks at 10 Khz in oneshot mode, amid 12
> Linux SCHED_FIFO, in USER SPACE as a nonroot user .
>
> The highest priority hard real time task measures its scheduling
> latency. After testing for 1 hour I got the following results:
> MAX JITTER 30 us,
> AVERAGE JITTER 10 us.
>
> The oneshot was not calibrated, if such you could have taken away some 7
> us from the above figures.
>
> The machine is a UP PII 233 Mhz.
>
> The test is running while I'm writing this message, with a good alpha
> response but with sluggish mouse based cut-pastes. Nonetheless by
> looking at the looping "cat /proc/interrupts" above I can see that my
> box is taking many hundreds of interrupts per second without any problem
> and the ping -f dots are below 3 lines.
>
> The result above can be obtained thank to a joint cooperative effort of
> a group of friends."
Can be verified immediatly by everybody, just dowload rtai-1.2. The
first working internal version has been operational within the
developper group since the beginning of this year and the first release,
rtai-x.xa, is dated Jan, 31st, 2000. It is not usefull only for cumpute
intensive tasks. It has been tested already in controlling profiling
brushless drivers at 2Khz directly from user space.
Ciao, Paolo.
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For more information on Real-Time Linux see:
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