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

[Cliff Frey]

Without knowing anything for sure, I suspect that your ethernet driver has a
bug in the transmit side when transmitting traffic faster than the wire
rate.

You could try a configuration like

InfiniteSource(LENGTH 1000) -> EtherEncap(...) -> Queue -> ToDevice;

and I imagine that you would see the same behavior.

You could also try plugging eth0 into a slower ethernet connection (10 or
100Mbps) and you might see the same behavior.

Are you running the most recent click sources (from git)?  There might have
been some ToDevice changes since then...

In any case, just my random ideas... I doubt that LinkUnqueue or Queue are
actually misbehaving.

Cliff

On Thu, Jan 21, 2010 at 2:07 PM, Sahan Gamage <sahans at gmail.com> wrote:

> 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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