Messages in this thread | | | From | Orin Eman <> | Subject | Re: 2.2.12: serial driver swapping characters?y | Date | Sat, 11 Sep 1999 02:38:13 -0700 (PDT) |
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> > >> 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.
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