Date: Mon, 2 Jan 1995 02:31:14 +1100 From: Bruce Evans <bde@zeta.org.au> To: hackers@freebsd.org, roberto@blaise.ibp.fr Subject: Re: Problem with sio ... Message-ID: <199501011531.CAA20306@godzilla.zeta.org.au>
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>I just upgraded my main machine (keltia) to 2.1-current and each time I send >something by UUCP (taylor, "i" protocol, bidirectionnal) I get that in >/var/log/messages : >Dec 31 21:35:45 keltia kernel: sio0: 304 more tty-level buffer overflows (total 1738) >Dec 31 21:35:48 keltia kernel: sio0: 570 more tty-level buffer overflows (total 2308) >... >I have that in /etc/rc.serial : > /bin/stty -f /dev/cuaia0 38400 crtscts > /bin/stty -f /dev/cuala0 38400 crtscts > /bin/stty -f /dev/ttyi00 38400 crtscts hupcl > /bin/stty -f /dev/ttyl00 38400 crtscts hupcl >How can I avoid the messages ? Increase TTYHOG in sys/tty.h, or maybe increase some of the ugly 512's in kern/tty.c. It would be interesting to know exactly why the overruns occur. They probably didn't occur in 2.0 because TTYHOG was not honored. They probably didn't occur in 1.1.x because TTYHOG was twice as large. The `rts' part of crtscts doesn't work in 2.0. This only matters if the modem supports output (from it) flow control, and anyway you want all buffers to be large enough so that rts flow control is never invoked. What size buffer does uccp use for reading? It has to be smaller than TTYHOG for blocking reads, enough so that (TTYHOG - buffer_size) can hold all the input that arrives while uucp is not running. This may be impossible if TTYHOG is too small :-]. The protocol window size only affects the problem indirectly. If the window is smaller than TTYHOG, then the sender won't be able to overrun the tty buffer. Bruce
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