On 10/01/14 15:47, Jesper Dangaard Brouer wrote:

Answer is yes.  It is very easy with simple netperf TCP_STREAM to cause
queueing >1 packet in the qdisc layer.

If that is the case, I withdraw any doubts i had.
Can you please specify this in your commit logs for patch 0?

If tuned (according to my blog,
unloading netfilter etc.) then a single netperf TCP_STREAM will max out
10Gbit/s and cause a standing queue.

You should describe such tuning in the patch log (hard to read
blogs for more than 30 seconds; write a paper if you want to provide
more details).

I'm monitoring backlog of qdiscs, and I always see >1 backlog, I never
saw a standing queue of 1 packet in my testing.  Either the backlog
area is high 100-200 packets, or 0 backlog.  (With fake pktgen/trafgen
style tests, it's possible to cause 1000 backlog).

It would be nice to actually collect such stats. Monitoring the backlog
via dumping qdisc stats is a good start - but actually keeping traces
of average bulk size is more useful.

cheers,
jamal