Carlos E. R. wrote:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
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.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.5 (GNU/Linux)
Comment: Made with pgp4pine 1.76
iD8DBQFGHYgxtTMYHG2NR9URAkOVAJ9ad/giFiYb4FBhi6J1ExI8bV4iogCeOECk
OF1MEQgQzc5PIziaXY0Ly94=
=nfXn
-----END PGP SIGNATURE-----
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: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
