Messages in this thread |  | | From | Roger Larsson <> | Subject | Re: Should I use Linux to develop driver for specialized ISA card? | Date | Tue, 4 Sep 2001 20:19:17 +0200 |
| |
On Tuesday den 4 September 2001 18:24, Christopher Friesen wrote: > Fred wrote: > > I'm curious, Alan, Why? I'm a hardware developer, and I would have > > assumed that linux would have been ideal for real time / embedded > > projects? (routers / controllers / etc.) Is there, for instance, a reason > > to suspect that linux would not be able to respond to interrupts at say > > 8Khz? > > of course I know nothing of rtlinux so I'll read. > > I'm involved in a project where we are using linux in an embedded > application. We've got a gig of ram, no hard drives, no video, and the only > I/O is serial, ethernet and fiberchannel. > > We have a realtime process that tries to run every 50ms. We're seeing > actual worst-case scheduling latencies upwards of 300-400ms. > > So while interrupts can be handled pretty quickly, you'll want to make sure > that your buffers are big enough that your userspace app only needs to run > every half second or so. > > You may be better off with rtlinux if you need better response. (Or if > you're on x86 hardware you could look at the low-latency patches.)
1) Why shouldn't the low-latency patches work for another architecture? Andrew Morton might be interested to fix other architectures too. (but most patches are not in architecture specific code)
2) Montavistas reschedulable kernel is a very interesting approach, newly released an update by Robert Love http://kpreempt.sourceforge.net/ http://tech9.net/rml/linux/patch-rml-2.4.10-pre2-preempt-kernel-1 (there are still some spikes, but the floor is smooth)
But note you with both approaches you want to run the latency critical process with a higher priority, and probably with the memory locked down.
See example code (latencytest) at: http://www.gardena.net/benno/linux/audio/ (but there is no need to run at the maximum possible priority since your process will be alone anyway...)
/RogerL
-- Roger Larsson Skellefteå Sweden - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |