Cost of enabling ALTQ in kernels

 	I have a couple of gateway boxes where I want to use ALTQ
 	(primarily for limited bandwidth to/from certain test
 	machines). In order to minimise custom kernel
proliferation
 	I'd like to just enable ALTQ in all kernels, but only
turn
 	it on on certain machines.

 	Is there any significant network performance or other
cost
 	in having ALTQ compiled into the kernel but not used?


-- 
 			   David Brownlee -- absabsd.org

On Sat, Jun 16, 2007 at 08:39:19PM +0100, David Brownlee
wrote:
> 	Is there any significant network performance or other
cost
> 	in having ALTQ compiled into the kernel but not used?

In the current world, yes. It can be improved to do either
of:
(1) One additional indirect functoin call per ifq
operation.
(2) One additional conditional branch per ifq operation.

The first choice shouldn't increase the size of the kernel
(might even
make it a bit smaller), the second would (very) slightly
increase it.

Joerg