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From: j@bonnie.heep.sax.de (J Wunsch)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: enabling remote dialup
Date: 4 Aug 1995 08:22:23 +0200
Organization: Private U**x site, Dresden.
Lines: 29
Message-ID: <3vseav$6ki@bonnie.tcd-dresden.de>
References: <3v3u2u$8v@goanna.cs.rmit.edu.au> <3v7em1$pu5@bonnie.tcd-dresden.de> <3vnmej$c9q@goanna.cs.rmit.edu.au>
Reply-To: joerg_wunsch@uriah.heep.sax.de
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Simon Harris <s9511800@yallara.cs.rmit.edu.au> wrote:
>Well actually my modem answers fine just my machine can't handle it and
>i get lots of "buffer overflow" messages from the kernel so I'm now down
>to an appalling 57600 :)
Do you use a FIFO UART?
What's the exact message? Do you get ``silo overflows'' or
``tty-level buffer overflows''? The former means that your line is
pushing bytes to the UART where the machine is too slow to answer the
UART's interrupt requests so the interrupt handler fails to drain all
characters. This is typically the case for non-FIFO UARTs. The
latter means the interrupt handler has been able to drain all bytes in
time, but he eventually ran out of tty buffers. Since the tty buffers
are being processed at splsofclock level, this basically means you've
got something that's raising the interrupt priority level for too
long, so the buffers are overflowing.
There are some kernel parameters that affect this behaviour, and it
might be necessary to tune the TTYHOG paramter on some slower
machines. While TTYHOG can be overridden from the kernel config file
for a -current kernel, you will have to modify it in /sys/sys/tty.h
directly for a system up to 2.0.5R.
--
cheers, J"org private: joerg_wunsch@uriah.heep.sax.de
http://www.sax.de/~joerg/
Never trust an operating system you don't have sources for. ;-)