Date: Tue, 24 Dec 1996 15:00:29 -0500 (EST) From: John D Duncan <jddst19+@pitt.edu> To: Antonio Bemfica <bemfica@militzer.me.tuns.ca> Cc: freebsd-questions@freebsd.org Subject: Re: silo overflows Message-ID: <Pine.GSO.3.95L.961224144617.19630B-100000@unixs5.cis.pitt.edu> In-Reply-To: <Pine.BSI.3.94.961223230436.11259B-100000@militzer.me.tuns.ca>
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Silo overflows exist when the machine cannot retrieve data from
the sio as fast as it is coming in, and so the UART sends a message
to the kernel, and the kernel records the retry. possible causes of
this problem are:
A slow machine
A heavily-loaded machine
A 16450 UART chip on the serial line, which should
be changed to a 16550A for unix
A low priority to the sio servicing compiled into the kernel.
An insanely high transfer rate set on cuaa1.
I use an AMD 5x86 on a 486 motherboard, with a SIIG card that has 16550s
on each line. My card was expensive to buy, and you can find a decent
multi-function card or serial board that provides these chips for about
10-30 bucks.
If you have these chips, and it's still slow, then you should find areas
of processor-intense computing and stop using them when doing important
serial work. The machine should be able to service the interrupts better
when you are not compiling, etc. Netscape itself caused problems for me
when I ran on 16450 uarts because of how processor-intensive it is.
If you aren't doing work, upgrade your processor.
If you have a fast processor, then there is a problem with your config.
If you need to do work while running serial, lets say your machine is a
combination news/ftp/ports server, and your processor is fast, then you
should look into a high-performance serial card that gives you a much
larger fifo on the uart. (fifo is the queue that the uart uses to fill
with unserviced data.) there are boards with a meg or more of fifo memory
on each line, or at least, there used to be.:) I think most basic fifos
are 16-64k. the reason why the 16450 is slow is that it only has a couple
of k on its buffer. I think it also has a poor block-transfer rate.
I believe that there are also dma serial cards that avoid these problems
well. there are a variety of options.
But right now, I only get silo overflows when I am using several programs
that use serial lines heavily, like ftp, news, and netscape.
cheerio-
John
==============
jddst19+@pitt.edu John Duncan
Freshman, University of Pittsburgh
"I'm not a doctor, but I ate one at the UPMC..."
On Mon, 23 Dec 1996, Antonio Bemfica wrote:
> I keep getting the following message while doing ftp transfers (I connect
> with user-ppp):
>
> /kernel: sio1: 1 more silo overflow (total xxx)
>
> The number (xxx) keeps growing ... Does anybody know why?
>
> Thanks
>
> Antonio
> --
> |Antonio Bemfica -------------------------- bemfica@militzer.me.tuns.ca ))
> |Halifax, Canada ------------------ http://militzer.me.tuns.ca/~bemfica ((
> |this message has no cash value - valid only at participating locations ))
> |not valid in combination with any other offer - sorry, no rain-checks ((
>
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