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Date: Thu, 16 Nov 1995 13:28:12 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199511160228.NAA29871@godzilla.zeta.org.au>
To: bde@zeta.org.au, hsu@cs.hut.fi
Subject: Re: ISP state their FreeBSD concerns
Cc: current@FreeBSD.ORG, j@uriah.heep.sax.de
Sender: owner-current@FreeBSD.ORG
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>Could it be sensible to make RS_IBUFSIZE ((TTYHOG)/4) ?  This would allow
>tuning TTYHOG value only.  It would be a kludge, though.  Maybe serial

Not very.  RS_IBUFSIZE is the fundamental quantity.  It should depend on
the driver and on the line speed and TTYHOG should depend on RS_IBUFSIZE
and the system load.  All the values should be variables but there has
to be some limit to stop unread input filling up all of memory.

> > 	RS_IBUFSIZE - 11520 * (1.0/hz + max_softtty_interrupt_latency) >= 0

>Btw, lots of ISDN "modems" like ZyXEL's are connected with overclocked
>16650/16550 serial ports.  I have one at 460.8k.

Does it have a higher clock speed or extra clocks?  Extra clocks aren't
supported (just as well they aren't as necessary as extra video clocks)
and you would have to increase various constants for flow control to
work and for good performance (output buffer sizes are a bit low but
can't be increased much because some of the buffers are on the kernel
stack...).

Bruce