Date: 8 Feb 1999 14:53:03 +1100 From: "John Saunders" <john.saunders@nlc.net.au> To: Stephen Rose <rose@dml.com> Cc: freebsd-current@FreeBSD.ORG Subject: Re: Silo overflow messages with 3.0 Release Message-ID: <19990208035303.9465.qmail@nhj.nlc.net.au> In-Reply-To: <Pine.BSF.4.05.9902061604510.18906-100000@locus.dml.com>
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Try the following patch. Look for a line in /sys/i386/isa/sio.c that
looks like:
com->fifo_image = t->c_ospeed <= 4800
? FIFO_ENABLE : FIFO_ENABLE | FIFO_RX_HIGH;
Replace FIFO_RX_HIGH with FIFO_RX_MEDH, and if that doesn't work try
FIFO_RX_MEDL instead.
This patch changes the RX FIFO trigger point from 12 down to 8 (or 4).
With it set to 12 the system only has 4 character periods to respond
to the IRQ. Normally a Pentium or higher should be able to handle
this, however things like SMP or non-DMA mode for your harddisk may
hold off interrupts for longer than normal. With it set to 8 there is
twice as long to process the IRQ before an overflow occurs.
Actually the sio driver should really detect silo overflows and drop
the FIFO level a notch automatically. Hmm, if I have some free time
I might look into it.
The bad side is that this patch increases the IRQ load on the box.
Although for a Pentium the serial processing load is a fraction of
a percent so double that is still negligable.
Cheers.
In nlc.lists.freebsd-current you wrote:
> I didn't get a response from the questions list, so let's try here.
> I've been getting my server ready to switch from FreeBSD 2.2.2 to 3.0
> Release. Everything was going well until I tried to bring my kernel ppp
> link up to my isp. I get many silo overflow messages when there's any
> activity on the line. The connection doesn't seem very responsive either.
> This machine is a dual pentium pro. I've built an smp kernel which seems
> to work fine otherwise. I've arranged to build the new system on another
> disk so I can easily switch between the 2.2.2 system and the 3.0 system.
> Everything works fine with 2.2.2. I've seen many messages in the archive
> about silo overflows, but there doesn't seem to be a real solution in
> them. Is this ever likely to work or should I just wait for 3.1?
> Steve Rose
> To Unsubscribe: send mail to majordomo@FreeBSD.org
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