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Date:      Tue, 21 Apr 1998 12:04:09 -0700 (PDT)
From:      Doug White <dwhite@gdi.uoregon.edu>
To:        Steve Sims <SimsS@IBM.Net>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: SILO Overflows
Message-ID:  <Pine.BSF.3.96.980421120116.4074Q-100000@gdi.uoregon.edu>
In-Reply-To: <000301bd6d21$cd6c0a00$64468094@Elvis.RatsNest.VaBeach.Va.Us>

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On Tue, 21 Apr 1998, Steve Sims wrote:

> Last week I installed a 56K/x2 USR Courier V.Everything internal modem in my
> puny 486/66 and have been seeing repeated "x more silo overflow (n total)"
> messages whenever the CPU gets even *slightly* loaded up.

I need the whole message here-- you left off the important part.  There
are two classes of these:

x more interrupt-level silo overflows
x more tty-level silo overflows

These point to problems with the kernel getting the data fast enough and a
user process getting the data fast enough, respectively.

> True Confession:  I took a couple of stabs at tweaking sio.c to set the fifo
> threshold lower, but after a while it dawned on me that tweaking the
> tx_fifo_size setting was NEVER going to help receive errors, so I gave up.
> D'oh!

You actually can tune the tx/rx buffer size.  You have a 16 byte buffer on
the 16550 and you can define the split between tx and rx.  So shrinking tx
will increase the rx and vice versa.

BTW, you *do* have a 16550 UART in there, right?

Your dmesg should report:

sio0 at 0x3f8-0x3ff irq 4 on isa
sio0: type 16550A

Doug White                              | University of Oregon  
Internet:  dwhite@resnet.uoregon.edu    | Residence Networking Assistant
http://gladstone.uoregon.edu/~dwhite    | Computer Science Major



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