Carlos E. R. wrote:
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The Tuesday 2007-04-10 at 17:27 +0200, Roger Oberholtzer wrote:
report data overruns. I also see missing characters in GPS data read over the serial port at this time.
Surprising... :-O
I get the point. But I do not think I have reached any resource limits when this happens. I know that is hard to judge. And I could be very wrong.
Yep. But it is indeed surprising that this could happen with current hardware. I wasn't even aware that it could happen. You see, if a plain 8086 could cope (barely) at 115000, a pentium should not even cough.
It might be worth a bugzilla report...
Another idea. There are some settings in the kernel about how fast is the task switcher clock and how interruptible are some tasks, and real time settings. Playing with that could help. I have found that some times, when a task is busy (mozilla!) the response to the keyboard is sluggish, might be related to your problem. I have been playing a little with those settings, but I'm not learned enough on linux kernels to recommend anything conclusive.
If hardware handshaking is impossible, revert to software handshake (much slower, chars have to be sent back)
But the software handshake must require that the driver is getting called in time, no?
Exactly; in your case it wouldn't be much use, or none at all. Mmmm...
- -- Cheers, Carlos E. R.
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Changing the HZ to 1000 would only impact on tasks running in the process context. The top-half of the interrupt handler runs in interrupt context. During the initial processing of an interrupt, the handler suspends other interrupts on the same IRQ. Remember this is character I/O, so there is going to be an interrupt for each character. The buffering of the data for a user application occurs in the bottom half of the interrupt handler. I forgot to ask if the GPS application reads the raw serial port, or uses a kernel module for gathering the data. Bill Anderson -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org