netdev - Re: [PATCH 2/2] pkt_sched: fq: fix pacing for small frames

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Date:	Fri, 15 Nov 2013 21:06:43 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, maze@...gle.com, willemb@...gle.com,
	ycheng@...gle.com, ncardwell@...gle.com
Subject: Re: [PATCH 2/2] pkt_sched: fq: fix pacing for small frames

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 15 Nov 2013 08:58:14 -0800

> From: Eric Dumazet <edumazet@...gle.com>
> 
> For performance reasons, sch_fq tried hard to not setup timers for every
> sent packet, using a quantum based heuristic : A delay is setup only if
> the flow exhausted its credit.
> 
> Problem is that application limited flows can refill their credit
> for every queued packet, and they can evade pacing.
> 
> This problem can also be triggered when TCP flows use small MSS values,
> as TSO auto sizing builds packets that are smaller than the default fq
> quantum (3028 bytes) 
> 
> This patch adds a 40 ms delay to guard flow credit refill.
> 
> Fixes: afe4fd062416 ("pkt_sched: fq: Fair Queue packet scheduler")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied and queued up for -stable.

Thanks.
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