device polling takes more CPU hits??

[Don Bowman]

From: James [mailto:haesu at towardex.com]

> 
> I have two boxes behind em0 that I can use to generate 
> 250kpps to another vlan
> within em0 card as a test, so that bge0 is not involved in 
> the stress test.
> Even when doing so, CPU load climbs higher with device 
> polling turned on.
> Opened up systat, etc to check the interrupts, and em0 is 
> generating 0 
> interrupts with device polling on (as obvious), but general 
> interrupt load
> climbs rock high.. so I don't know what's causing it to 
> climb. Cleared the
> firewall rules as well as a test... no difference :(
> 
> Oh also, just FYI, each vlan interface has link0 set, since 
> em(4) supports
> hardware 802.1q tag/detagging.
> 

The CPU time during the 'polling' is charged to interrupt,
even though it occurs during softclock. That's why you
see 0 interrupts, but high CPU usage in interrupt.
Did u try lowering the 'register' access?

--don