Date: Fri, 15 Dec 1995 15:36:49 -0500 (EST) From: "Stephen F. Combs" <combssf@salem.ge.com> To: bde@zeta.org.au, nate@rocky.sri.MT.net Cc: FreeBSD-hackers@FreeBSD.org Subject: Re: sio overruns on 2.0.5R Message-ID: <199512152036.PAA26801@combs.salem.ge.com>
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> From owner-freebsd-hackers@freefall.freebsd.org Fri Dec 15 15:29:45 1995 > Date: Fri, 15 Dec 1995 12:06:07 -0700 > From: Nate Williams <nate@rocky.sri.MT.net> > To: Bruce Evans <bde@zeta.org.au> > Cc: nate@rocky.sri.MT.net, FreeBSD-hackers@FreeBSD.org > Subject: Re: sio overruns on 2.0.5R > In-Reply-To: <199512151859.FAA26342@godzilla.zeta.org.au> > Sender: owner-hackers@FreeBSD.org > Content-Length: 841 > > > >> After I switched to a Asus P55TP4XE 90Mc I see things like > > >> > > >> sio0: 5 more silo overflows (total 7) > > > > >I hate to sound like a broken record, but are you *sure* you're using > > >flow-control? Can you use stty on the connected end to make sure? > > > > Er, flow control has no effect on silo overflows. > > Really? If a machine doesn't provide flow control can't you over-run > the buffers if the machine gets loaded down and the interrupt load gets > so bad that the sio interrupt handler isn't called enough. However, if > you use flow control shouldn't it stop the buffer from getting > overflowed simply because no more data is being received. > > Am I totally out to lunch here? I know that I get lots of silo > over-flows when I don't use flow control and push the line fast, where > as soon as I turn on flow control they go away. > > > Nate > Unless the FreeBSD team responsible for the 'sio' driver has made ENORMOUS changes since the last time I looked at it (quite a while ago!?!), flow control DOES affect silo-overruns! Flow-Control provides a throttle, limiting the chances of a silo-overrun (not eliminating it, just limiting it). The modem/printer/mouse/other computer attached to the sio port MUST respect the STOP flow-control signal within a reasonable amount of time (a few, 2-4, character transmission times, usually) for flow-control to be effective, but, most modern pieces of equipment do. Steve Combs
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