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Date:      Thu, 21 Jan 1999 11:27:47 +1100 (EST)
From:      "John Saunders" <john.saunders@nlc.net.au>
To:        Wes Peters <wes@softweyr.com>
Cc:        Ruslan Ermilov <ru@ucb.crimea.ua>, freebsd-stable@FreeBSD.ORG
Subject:   Re: Kernel PPP tty-level buffer overflows
Message-ID:  <Pine.LNX.3.95.990121111934.29987A-100000@nhj.nlc.net.au>
In-Reply-To: <36A60EF7.53A03129@softweyr.com>

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On Wed, 20 Jan 1999, Wes Peters wrote:

> > > > > sio0: 815 more tty-level buffer overflows (total 4715)
> > > > > sio0: 3093 more tty-level buffer overflows (total 7808)
> > Read the sio(4) manpage, section ``BUGS''.
> > Try to lower down your port's baud rate, say to 57600bps.
> 
> Or get a 16650 or 16750 based card.  I have a dual 16C650 card
> in my dial-in server, running two Impact IQ ISDN adapters at
> 115,200 bps, and have had no problems whatsoever.  One of these
> days I'm going to figure out how to crank them up to 230,400
> bps.

It's got nothing to do with the UART, a 16550A can run all day at 115200
under FreeBSD. If the problem was the UART then the error would be "silo
overflow". The problem is that the the tty driver is delivering data too
quickly for PPP to handle. 

I'm still convinved that a larger buffer may help, this needs some
investigation. The machine is a Pentium 120 with 64MB of RAM, so it's not
exactly slow, and it's not swapping. So if it can manage to keep a 10Mbps
ethernet saturated why is it having problems with a 115200 com port? And
when I'm not FTP'ing stuff to it the ethernet is running around 7%
utilization. 

Anyway running 57600 seems to cure the problem.

Cheers.
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