Date: Mon, 19 Jun 1995 02:59:08 +0300 From: Heikki Suonsivu <hsu@clinet.fi> To: Bruce Evans <bde@zeta.org.au> Cc: hsu@clinet.fi, current@freebsd.org Subject: Re: kern/528: interrupt-level buffer overflows Message-ID: <199506182359.CAA03497@katiska.clinet.fi> In-Reply-To: <199506180946.TAA22668@godzilla.zeta.org.au> References: <199506180946.TAA22668@godzilla.zeta.org.au>
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Bruce Evans writes:
> >Jun 18 05:14:47 pommi /kernel: sio1: 119 more interrupt-level buffer over
> >flows (total 3642)
> >Jun 18 05:14:47 pommi /kernel: sio1: 119 more interrupt-level buffer overflows (
> >total 3642)
> For this to happen, softclock() must sometimes be delayed for a long time
> several clock ticks (about 3 clock ticks for 119 characters at 38400 bps
> and about (256 - 38) / 38 clock ticks for filling up the 256 character
> buffer before that.
> >>Fix:
> Use hardware handshaking.
Its a leased line, no hardware handshake. WIth decent uarts it shouldn't a
problem to run even at 115k (It did work with Linux on 386/16 and FreeBSD
on 486/66, about 11kbytes per second for ftp transfer).
I can think of increasing the serial buffers (256 characters sounds low)
and if the problem is interrupt latency, dropping the trigger level on
uarts. Any ideas?
> I've heard that some systems 20 times as fast as a 386/16 are too slow for
> a 38400 bps link.
With 16550's? Less than 300 interrupts per second?
--
Heikki Suonsivu, T{ysikuu 10 C 83/02210 Espoo/FINLAND,
hsu@cs.hut.fi home +358-0-8031121 work -4375209 fax -4555276 riippu SN
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