Re: 2.2.12: serial driver swapping characters?y
Orin Eman (orin@nwlink.com)
Sat, 11 Sep 1999 02:38:13 -0700 (PDT)
>
> >> I just saw the first instance of what might be serial corruption last night
> >> running 2.3.16. The kernel dumped "VJ Decompression Error" onto my console
> >> while I was using PPP over an error-correcting modem link. I have no idea if
> >> this was due to the serial stream or something in the TCP layer; but if the
> >> former, and the serial code from 2.3 was back-ported to 2.2, then perhaps the
> >> errors are related.
> >
> >Let me throw in that the problem did not occur on a faster machine,
> >so there might be some race conditions. Slow hardware can't explain
> >swapped chracters or duplicated ones IMHO.
> >
> >Anyone with a real slow machine out there?
> >
>
> I have a PS/2 486SLC which is a 17 bogomip machine. I am having a lot
> of problems with PPP throughput since moving up from 2.2.10 to 2.2.12.
> At times I see up to 50% incoming PPP frame errors over a V90 modem
> link.
Probably. Check for overrun errors - in /proc/tty/driver/serial - they
show as oe:. For example, I see
0: uart:16550A port:3F8 irq:4 baud:115200 tx:0 rx:61213 oe:5
5 overrun errors. Not surprising at 115200 baud on a K6-2 300???
Well, I had an incoming stream at 115200 and it could display
fine - until there was disk activity... when I would get the errors.
To drop characters on a 16550 even at 115200 baud requires interrupts
to be blocked for a long time.
I have tried the irqtune program which rearranges the IRQ priorities
and using it, I have received hundreds of MB of data with only
a few overrun errors. However, I'm not sure of the safety of
this program. It worked for me.
Orin.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/