Router take advantage of device polling

Matthew Seaman m.seaman at
Sat May 22 05:08:45 PDT 2004

On Sat, May 22, 2004 at 06:51:32AM -0400, Jeffrey Lyon wrote:
> I am currently running a router pushing about 15 megabit of traffic, 
> with CPU usage like so:
> root     25  5.9  0.0     0   12  ??  WL   10:16AM  47:49.70  (irq7: 
> bge0 amr0)
> root     14  5.9  0.0     0   12  ??  WL   10:16AM  55:15.63  (swi1: net)
> root     26  3.0  0.0     0   12  ??  LL   10:16AM  28:42.81  (irq5: bge1)
> I am told that activating the device_polling kernel option will cause a 
> substantial reduction in this usage. Is there any truth to that statement?

Probably not.  I see you are using bge(4) devices -- there's nothing
in the polling(4) or bge(4) man pages to suggest that the bge
interface does support polling, and the code in /usr/src/sys/dev/bge
makes no reference to the DEVICE_POLLING cpp macro, so it's unlikely
to help with that hardware.

Assuming you've got suitable hardware, whether device polling gains
you much, or anything at all depends on the nature of the traffic
you're dealing with.  There are about dozen kernel tunables that you
can use to optimize traffic flows. See the polling(4) man page for
more information.



Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
                                                      Savill Way
PGP:         Marlow
Tel: +44 1628 476614                                  Bucks., SL7 1TH UK
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