em driver input errors

[alexpalias-bsdnet at yahoo.com]

--- On Fri, 9/4/09, Adrian Penisoara <ady at freebsd.ady.ro> wrote:

> From: Adrian Penisoara <ady at freebsd.ady.ro>
> Subject: Re: em driver input errors
> To: alexpalias-bsdnet at yahoo.com
> Cc: freebsd-net at freebsd.org
> Date: Friday, September 4, 2009, 5:11 PM
> Hi,

Hello

> First question that comes to mind is: have you tried device
> polling ?
> Looking up the thorough decscription you made it appears
> not to.

Yes, I did try it.  I mentioned it in a followup mail (I had scheduled maintenance one week from my first message, and with that occasion I booted a kernel with support for polling).

The polling only increased latency, and got me way more errors, and more consistently.  If you look at the graphs linked below, instead of having those 35 errors/sec spikes several times per day, I was constantly exceeding 100 errorrs/s, with no error-free parts.

I will admit I only had HZ=1000 in the kernel config file.

The next step will probably be trying 8.0-RELEASE after it seems stable enough on a test machine.

I might try setting polling mode back on for a few hours, and posting graphs.


Links to the errors/s and packets/s graphs:
http://www.dataxnet.ro/alex/errors.png
http://www.dataxnet.ro/alex/packets.png

> Please check the polling(4) manual page and Luigi's page
> [1] for
> detailed information. Basically it switches the device
> driver from
> interrupt mode to polling mode, allowing to specify the
> user/system
> CPU usage fraction.
> 
> [1] http://info.iet.unipi.it/~luigi/polling/
> 
> Regards,
> Adrian Penisoara
> EnterpriseBSD


Thanks for the help
Alex