[vortex] 3c59x network driver question

[Jonathan Lynch]

I have 3 network interface cards in a linux router using version 2.6.12 of the kernel. I use two
interface cards for incoming traffic and one for outgoing traffic. The two cards used for incoming
traffic, eth1 and eth2, are 3com network cards that use the 3c59x driver. The card that is used for
outgoing traffic uses the e1000 driver. The following is the output from /proc/interrupts and lspci.

           CPU0
  0:  299823889          XT-PIC  timer
  1:     173520          XT-PIC  i8042
  2:          0          XT-PIC  cascade
  5:     126665          XT-PIC  Intel ICH5
  8:      58667          XT-PIC  rtc
  9:   22162271          XT-PIC  acpi, ehci_hcd:usb1, uhci_hcd:usb2, uhci_hcd:usb5,
i915 at pci:0000:00:02.0, eth2
 10:   46703995          XT-PIC  libata, uhci_hcd:usb4, eth0
 11:   44809773          XT-PIC  uhci_hcd:usb3, eth1
 12:    4199807          XT-PIC  i8042
 14:     547056          XT-PIC  ide0
 15:    2696779          XT-PIC  ide1
NMI:          0
ERR:          0



03:05.0 Ethernet controller: 3Com Corporation 3c905 100BaseTX [Boomerang]
03:07.0 Ethernet controller: 3Com Corporation 3c905 100BaseTX [Boomerang]

3:05.0 Class 0200: 10b7:9050
03:07.0 Class 0200: 10b7:9050


I loaded the module "options 3c59x debug=7,debug=7" in /etc/modprobe.conf to help me follow the
code. sample output from dmesg

boomerang_interrupt. status=0x8401
eth1: interrupt, status 8401, latency 5 ticks.
eth1: In interrupt loop, status 8401.
boomerang_interrupt->boomerang_rx
boomerang_rx(): status 8001
Receiving packet size 1514 status 85ea.
eth1: exiting interrupt, status 8000.



I have followed it up all the way to netif_rx() and have a few questions and would appreciate if
someone could answer them.

what does the register RxDComplete mean ?. The function boomerang_rx() loops on its value to take
packets of the rx ring buffer. Does this mean that while there are still packets in the rx ring the
interrupt handler will pass them up to upper layers ?

I have notcied that a lot of delay is introduced in the router due to the way packets from both
incoming interfaces end up in the output queue.

When there are two network interfaces mainly receiving packets and one mainly sending, will their
interrupt number affect how the order packets are put into the queue for transmission? Are
interrupts prioritised ie if packets arrive at both eth1 and eth2 at the same time, will the packets
from eth2 be passed to upper layers first because it has a lower interrupt number?

Are packets received from both network devices put into the same softnet queue for the 1 cpu?


Again, I would really appreciate if someone could answer my question.


Jonathan Lynch