[Click] Problem with click fake-router.click and delay elements

[Sahan Gamage]

Hi All,

I was working with click router to implement a delay inducing network.
What I wanted was to configure a click router with standard routing
components and once the routing is done, add some extra delay
(specified). So I modified the fake-router.click to include real
network devices (which is much similar to the router discussed in SOSP
99 paper). I encountered two problems.
1. When I ran the router without delay elements and use an iperf
client and server on the two sides of the router, the maximum
throughput I got was 330Mbps. The network drivers were tg3 drivers. My
feeling is that the throughput is somewhat lower than that is
expected.

2. Then I changed the configuration a little bit to introduce delays.
What I did was change the output component from:
out0 :: Queue(2000) -> ToDevice(eth0)
to
out0 :: Queue(2000) -> LinkUnqueue(0.005s, 1000Mbps) -> Queue(2000) ->
ToDevice(eth0).

I did this for both eth0 and eth1.
But when I ran this configuration, the machine always locks up.
Sometimes I can see there's a log entry in kernel message log saying
"tg3: eth1: BUG! Tx Ring full when queue awake!".  Few  options I
tried :
 - I tried different delay elements such as LinkUnqueue and DelayUnqueue.
 - I tried different Queue sizes (from 200 to 5000).
 - I changed the Tx ring size of the devices to 511 (maximum allowed).

But none of them resolved the problem.

My feeling is the crash (or the lockup) is primarily due to the delay
introducing elements (LinkUnqueue or DelayUnqueue). Does anybody know
the reasons for reduced performance numbers and the lockups ?

(I have attached my configuration file along with this)

Thanks in advance
-sahan
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