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Date: Thu, 09 Oct 2003 03:18:30 -0700
From: Terry Lambert <tlambert2@mindspring.com>
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To: "Michael O. Boev" <mike@tric.tomsk.gov.ru>
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Subject: Re: Why is em nic generating interrupts?
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"Michael O. Boev" wrote:
> I've got a [uniprocessor 5.1-RELEASE] router machine with fxp and em nics.
> I've built my kernel with the following included:
> 
> options         DEVICE_POLLING
> options         HZ=2500
> 
> and enabled polling in /etc/sysctl.conf.
[ ... ]
> What's happening? Is polling working in my case?
> If yes, why is vmstat showing interrupts? I see clearly,
> that fxp's counter doesn't increase, and em's is constantly growing.
> 
> Is there anyone who knows for sure that em's polling works?

You may want to ask Luigi; polling is his code.

However, I believe the issue is that polling doesn't start
until you take an interrupt, and it stops as soon as there is
no more data to process, and waits for the next interrupt.

If you were to jack your load way up, you would probably see
an increase in interrupts, then them dropping off dramatically.

If all else fails, read the source code... 8-).

-- Terry