[Click] MSQueue induced latency

[Beyers Cronje]

Hi,

As with my previous email I'm running a simple switch configuration:

sw :: EtherSwitch;        //MT enabled etherswitch
out0 :: MSQueue -> ToDevice(eth0);
out1 :: MSQueue -> ToDevice(eth1);
PollDevice(eth0, PROMISC true) -> [0]sw;
PollDevice(eth1, PROMISC true) -> [1]sw;
sw[0] -> out0; 
sw[1] -> out1;

I've compiled click with multithreading enabled and using
click-install with the -t option.
When doing a ping through the switch between two devices located on
segments directly conencted to eth0 and eth1 I get an average ping
time of 25ms. This is obviously way too high.

Using the same setup replacing only MSQueue with CPUQueue (or even
simple Queue under single thread Click) I get an average ping time of
<1ms.

Another test involved copying a 500MB file between the two end
devices. With MSQueue I got an average of around 6MB per second, while
with CPUQueue I got over 9MB per second.

Any idea why MSQueue will introduce so much latency?

Kind regards

Beyers