em0, polling performance, P4 2.8ghz FSB 800mhz

[Mike Tancsa]

At 09:38 PM 29/02/2004, Don Bowman wrote:
>From: Mike Tancsa [mailto:mike at sentex.net]
> > 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.
>I picked 2500 as the best for my system. Its higher than
>allowed by rfc1323 and PAWS [kern/61404], but not by so much
>that i anticipate a problem.

Do you run the box with the supplied patch ?  On the firewall device I was 
thinking of experimenting with, I do have long TCP sessions that it sounds 
like HZ=2500 would break.


>For my target packets per second
>rate, it means that i can use a reasonable number of dma
>descriptors. I found that bridging performance in particular
>needs the higher hz to avoid dropping packets, to improve
>its performance.

In terms of fiddling with the em tunables, what are the drawbacks of moving 
from 256 to 512 on

EM_MAX_TXD
EM_MAX_RXD

>more buffers == better ability to handle latency
>bursts, but worse for cache occupancy.

Buffers as is net.inet.ip.intr_queue_maxlen ?

Thanks,

         ---Mike