device polling takes more CPU hits??

[James]

Hi all,

I've got a weird case on my hands on a 2.8ghz xeon w/ HTT working as a router w/
device polling... This is a single-processor 2.8ghz xeon, not dual/quad, etc.
The kernel does have SMP compiled in though.

The box has two gig-e cards, em0 and bge0. bge0 is the uplink to the core,
em0 is the downlink to the ethernet switch with 802.1q vlans for customer
aggregation. During daytime, the box pushes about 15kpps at rate of roughly
12% interrupt CPU load. Sometimes when it spikes to 100kpps (rare, but happens),
cpu load goes up as high as 30% on interrupts.

Now these figures are w/ device polling off. As soon as I turn device polling
ON, interrupt load climbs from 12% to 23%. During spikes, it climbs to about
48% to 50%. 

Any idea why device polling is kind of having... negative impact? Is this b/c
I have SMP compiled on a box that really doesn't have two cpu's?? Is SMP+APIC_IO
support even required for HTT use?

The version btw is FreeBSD 4.9-STABLE.

hardware info:
Jul 21 23:09:24 r2.bos /kernel: CPU: Intel(R) Xeon(TM) CPU 2.80GHz (2788.16-MHz 686-class CPU)
Jul 21 23:09:24 r2.bos /kernel: Origin = "GenuineIntel"  Id = 0xf29  Stepping = 9
Jul 21 23:09:25 r2.bos /kernel: em0: <Intel(R) PRO/1000 Network Connection, Version - 1.7.25> port 0xccc0-0xccff mem 0xfcd00000-0xfcd3ffff,0xfcd40000-0xfcd5ffff irq 7 at device 6.0 on pci3
Jul 21 23:09:25 r2.bos /kernel: bge0: <Broadcom BCM5704C Dual Gigabit Ethernet, ASIC rev. 0x2002> mem 0xfcf20000-0xfcf2ffff,0xfcf30000-0xfcf3ffff irq 2 at device 0.0 on pci2
Jul 21 23:09:25 r2.bos /kernel: bge1: <Broadcom BCM5704C Dual Gigabit Ethernet, ASIC rev. 0x2002> mem 0xfcf00000-0xfcf0ffff,0xfcf10000-0xfcf1ffff irq 5 at device 0.1 on pci2

Thanks for any tips!
-J 
-- 
James Jun                                            TowardEX Technologies, Inc.
Technical Lead                        Network Design, Consulting, IT Outsourcing
james at towardex.com                  Boston-based Colocation & Bandwidth Services
cell: 1(978)-394-2867           web: http://www.towardex.com , noc: www.twdx.net