Re: Why is em nic generating interrupts?

On Thursday 09 October 2003 05:57 am, Michael O. Boev wrote:
> > -----Original Message-----
> > From: Terry Lambert [mailto:tlambert2_at_mindspring.com]
> > Sent: Thursday, October 09, 2003 5:19 PM
> > To: Michael O. Boev
> > Cc: freebsd-current_at_FreeBSD.ORG
> > Subject: Re: Why is em nic generating interrupts?
> >
> > "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.
>
> To this dare I object, that there is traffic going through this machine,
> and fxp0 is NOT generating interrupts, while em IS. So, if the rule above
> works, they both have to behave in same ways.
>
> > If all else fails, read the source code... 8-).
>
> )) I've tried to, but... had to ask here. So all is left is to ask Luigi
> and Intel.

I cannot comment on 5.1-R, but I am running DEVICE_POLLING tests today with 
-current and 2 em NICS and systat -vm shows no interrupts for the IRQs where 
the NICs are.  I can only guess that either 5.1-R has a bug or the polling 
support was not in the driver at that point.

	Sam