netdev - Re: [RFC PATCH v2] tcp: TCP Small Queues

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Date:	Thu, 12 Jul 2012 15:46:52 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	John Heffner <johnwheffner@...il.com>
Cc:	David Miller <davem@...emloft.net>, ycheng@...gle.com,
	dave.taht@...il.com, netdev@...r.kernel.org,
	codel@...ts.bufferbloat.net, therbert@...gle.com,
	mattmathis@...gle.com, nanditad@...gle.com, ncardwell@...gle.com,
	andrewmcgr@...il.com
Subject: Re: [RFC PATCH v2] tcp: TCP Small Queues

On Thu, 2012-07-12 at 09:33 -0400, John Heffner wrote:
> One general question: why a per-connection limit?  I haven't been
> following the bufferbloat conversation closely so I may have missed
> some of the conversation.  But it seems that multiple connections will
> still cause longer queue times.

We already have a per-device limit, in qdisc.

If you want to monitor several tcp sessions, I urge you use a controller
for that. Like codel or fq_codel.

Experiments show that limiting to two TSO packets in qdisc per tcp flow
is enough to stop insane qdisc queueing, without impact on throughput
for people wanting fast tcp sessions.

Thats not solving the more general problem of having 1000 competing
flows.

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