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To: "Willem Jan Withagen" <wjw@withagen.nl>
From: Ian FREISLICH <if@hetzner.co.za>
In-Reply-To: Message from "Willem Jan Withagen" <wjw@withagen.nl> 
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Date: Mon, 02 Aug 2004 14:10:29 +0200
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cc: current@FreeBSD.ORG
Subject: Re: LPT interruptstorm 
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"Willem Jan Withagen" wrote:
> From: "Ian FREISLICH" <if@hetzner.co.za>
> > "Willem Jan Withagen" wrote:
> > > Hi,
> > >
> > > Must be a FAQ, but I did not find anything ...
> > >
> > > When wanting to print thru /dev/lpt0 the kernel now starts to
> > > complain about interruptstorms. Something I can imagine, since
> > > printing can generate > 1000 ints/sec.  Problem is that the
> > > current document (500k) is now printed at 100 interrupts/sec.
> > >
> > > That's going to take some time....
> > > How do I prevent this from happening?
> >
> > /etc/sysctl.conf: hw.intr_storm_threshold=2000
> >
> > OR
> >
> > /boot/device.hints: hint.ppc.0.flags="0x8"
> >
> > Make sure your bios is set to ecp/epp for the printer port, or the
> > second option will fail.  A couple of people around here have also
> > suggested 'lptcontrol -e', but every time I've tried that (even with
> > lpd stopped) I get 'lptcontrol: open: Device busy'.  I'm not sure
> > what keeps the printer port open other than lpd.
>
> Setting the sysctl worked.  But now watching it with sysstat, I see
> that the interrupts go up as high as 65.000 ????

Yes, I was seeing ~43000/second on my PII.  If you set the hint, I
think it will use DMA to do the transfer with periodic interrupts
to fill the buffer.

Ian

--
Ian Freislich