netdev - Re: [PATCH net-next] netem: use rb tree to implement the time queue

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Message-Id: <20130701.180804.2068659449166342971.davem@davemloft.net>
Date:	Mon, 01 Jul 2013 18:08:04 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, stephen@...workplumber.org
Subject: Re: [PATCH net-next] netem: use rb tree to implement the time queue

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 28 Jun 2013 07:40:57 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Following typical setup to implement a ~100 ms RTT and big
> amount of reorders has very poor performance because netem
> implements the time queue using a linked list.
> -----------------------------------------------------------
> ETH=eth0
> IFB=ifb0
> modprobe ifb
> ip link set dev $IFB up
> tc qdisc add dev $ETH ingress 2>/dev/null
> tc filter add dev $ETH parent ffff: \
>    protocol ip u32 match u32 0 0 flowid 1:1 action mirred egress \
>    redirect dev $IFB
> ethtool -K $ETH gro off tso off gso off
> tc qdisc add dev $IFB root netem delay 50ms 10ms limit 100000
> tc qd add dev $ETH root netem delay 50ms limit 100000
> ---------------------------------------------------------
> 
> Switch netem time queue to a rb tree, so this kind of setup can work at
> high speed.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Stephen Hemminger <stephen@...workplumber.org>

Looks good, nice work Eric, applied.

Let's see how long that skb->{prev,next} trick holds up ;-)
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