Re: [RFC v2] fq_codel : interval servo on hosts

On Tue, 2012-09-04 at 08:10 -0700, Nandita Dukkipati wrote:

The idea of using srtt as interval makes sense to me if alongside we
also hash flows with similar RTTs into same bucket. But with just the
change in interval, I am not sure how codel is expected to behave.

My understanding is: the interval (usually set to worst case expected
RTT) is used to measure the standing queue or the "bad" queue. Suppose
1ms and 100ms RTT flows get hashed to same bucket, then the interval
with this patch will flip flop between 1ms and 100ms. How is this
expected to measure a standing queue? In fact I think the 1ms flow may
land up measuring the burstiness or the "good" queue created by the
long RTT flows, and this isn't desirable.

Well, how things settle with a pure codel, mixing flows of very
different RTT then ?

It seems there is a high resistance on SFQ/fq_codel model because of the
probabilities of flows sharing a bucket.

So what about removing the stochastic thing and switch to a hash with
collision resolution ?