netdev - Re: [Codel] [RFC v2] fq_codel : interval servo on hosts

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Date:	Tue, 04 Sep 2012 17:39:09 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jonathan Morton <chromatix99@...il.com>
Cc:	Nandita Dukkipati <nanditad@...gle.com>,
	Tomas Hruby <thruby@...gle.com>,
	netdev <netdev@...r.kernel.org>,
	"codel@...ts.bufferbloat.net" <codel@...ts.bufferbloat.net>
Subject: Re: [Codel] [RFC v2] fq_codel : interval servo on hosts

On Tue, 2012-09-04 at 18:25 +0300, Jonathan Morton wrote:
> I think that in most cases, a long RTT flow and a short RTT flow on
> the same interface means that the long RTT flow isn't bottlenecked
> here, and therefore won't ever build up a significant queue - and that
> means you would want to track over the shorter interval. Is that a
> reasonable assumption?
> 

This would be reasonable, but if we have a shorter interval, this means
we could drop packets of the long RTT flow sooner than expected.

Thats because the drop_next value is setup on the previous packet, and
not based on the 'next packet'

Re-evaluating drop_next at the right time would need more cpu cycles.


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