On Mon, Mar 20, 2000 at 01:30:31PM +0100, David Olofson wrote:
> Sat, 18 Mar 2000 Alain Rollé wrote:
> > To end with, one more question :
> > In the RTL manifesto is stated that :
> > "You can have deterministic worst case behaviour time on Solaris RT, but the
> > worst case is really worse than you might be willing to tolerate"
> > Can anyone give me an indication of the worst case time between the moment a
> > hardware interrupt is detected by the processor and the moment an interrupt
> > handler starts to execute with Solaris RT. I can't seem to find these figures
> > on the sun site.
>
> Well, I had a look, and I can't find anything but "...in a future version of
> this document." Where are the figures? I actually thought Solaris had hard RT,
> thanks to their brutal rape of their kernel (ie making it fully preemptive),
> but if it's hard to find the figures (if they exist), one starts to wonder if
> they're hiding something...
I saw them quote 2ms on a dual with some odd configuration,
> Anyway, AFAIK, their solution is basically meant for real time multimedia and
> that kind of stuff, which means that worst case latencies in the ms range are
> acceptable. We're not dealing with latencies in the same order of magnitude as
> RTLinux, QNX and other dedicated RT solutions. You just can't get that
> throughout the system without compromising non-RT performance.
>
> With Linux + lowlatency (hard RT for user space), we are pretty certain that we
> can guarantee sub ms latencies for SCHED_FIFO threads on correctly configured
> P133+ systems, and we're still dealing with a non-preemptive kernel. If
I'd love to see a solid timing study showing that. Can you do
ping -f someone &
while true; do tar cf /dev/null /dev/hda_x ; done; &
while true; do make -j 4 bzImage ; done; &
and still get sub ms latencies?
That would be cool.
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