em0, polling performance, P4 2.8ghz FSB 800mhz

[Mike Tancsa]

At 08:44 PM 29/02/2004, Don Bowman wrote:
>From: Mike Tancsa [mailto:mike at sentex.net]
> >
> > On Sat, 28 Feb 2004 23:17:44 -0500, in sentex.lists.freebsd.hackers >
> > >If you want to spend more time in kernel, perhaps change
> > >
> > >I might have HZ @ 2500 as well.
> >
> > Hi,
> >       Just curious as to the reasoning behind that ?
>
>@ high packet rates, you don't have enough DMA
>queues available to the em driver, and will drop.
>increasing the number of dma buffers will cause
>problems with cache occupancy. Increasing the HZ
>doesn't have a huge cost.

But why that value ? Did you determine it by trial and error or deduce it 
based on some other factors ?  Also, is this value optimal for fxp based boxes.

         ---Mike