netdev - Re: [PATCH] netem: fix rate extension and drop accounting

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Date:	Tue, 03 Jul 2012 11:54:17 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>,
	Hagen Paul Pfeifer <hagen@...u.net>,
	Yuchung Cheng <ycheng@...gle.com>,
	Andreas Terzis <aterzis@...gle.com>,
	Mark Gordon <msg@...gle.com>
Subject: Re: [PATCH] netem: fix rate extension and drop accounting

On Tue, 2012-07-03 at 11:25 +0200, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> commit 7bc0f28c7a0c (netem: rate extension) did wrong maths when packet
> is enqueued while queue is not empty.
> 
> Result is unexpected cumulative delays
> 
> # tc qd add dev eth0 root est 1sec 4sec netem delay 200ms rate 100kbit
> # ping -i 0.1 172.30.42.18
> PING 172.30.42.18 (172.30.42.18) 56(84) bytes of data.
> 64 bytes from 172.30.42.18: icmp_req=1 ttl=64 time=208 ms
> 64 bytes from 172.30.42.18: icmp_req=2 ttl=64 time=424 ms
> 64 bytes from 172.30.42.18: icmp_req=3 ttl=64 time=838 ms
> 64 bytes from 172.30.42.18: icmp_req=4 ttl=64 time=1142 ms
> 64 bytes from 172.30.42.18: icmp_req=5 ttl=64 time=1335 ms
> 64 bytes from 172.30.42.18: icmp_req=6 ttl=64 time=1949 ms
> 64 bytes from 172.30.42.18: icmp_req=7 ttl=64 time=2450 ms
> 64 bytes from 172.30.42.18: icmp_req=8 ttl=64 time=2840 ms
> 64 bytes from 172.30.42.18: icmp_req=9 ttl=64 time=3121 ms
> 64 bytes from 172.30.42.18: icmp_req=10 ttl=64 time=3291 ms
> 64 bytes from 172.30.42.18: icmp_req=11 ttl=64 time=3784 ms
> 
> This patch also fixes a double drop accounting in case packet is dropped
> in tfifo_enqueue()
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Yuchung Cheng <ycheng@...gle.com>
> Cc: Andreas Terzis <aterzis@...gle.com>
> Cc: Mark Gordon <msg@...gle.com>
> Cc: Hagen Paul Pfeifer <hagen@...u.net>
> ---

Hmm, I'll send a v2





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