netdev - Re: [PATCH iproute2] tc_codel: Controlled Delay AQM

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Message-ID: <CAA93jw5oOz38UHsp2UODJcbn9uDz34RfPSNCE-qE-7BKoshLtA@mail.gmail.com>
Date:	Tue, 22 May 2012 16:59:48 -0700
From:	Dave Taht <dave.taht@...il.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	netdev <netdev@...r.kernel.org>,
	Dave Taht <dave.taht@...ferbloat.net>
Subject: Re: [PATCH iproute2] tc_codel: Controlled Delay AQM

I promised eric I'd write the two man pages.

I also promised myself a vacation. The last year has been a long hard
road. If someone
hasn't got to writing the man pages by the time I get back from lupin,
I'll write it.

On Tue, May 22, 2012 at 2:16 PM, Stephen Hemminger
<shemminger@...tta.com> wrote:
> On Fri, 11 May 2012 08:22:35 +0200
> Eric Dumazet <eric.dumazet@...il.com> wrote:
>
>> From: Eric Dumazet <edumazet@...gle.com>
>>
>> An implementation of CoDel AQM, from Kathleen Nichols and Van Jacobson.
>>
>> http://queue.acm.org/detail.cfm?id=2209336
>>
>> This AQM main input is no longer queue size in bytes or packets, but the
>> delay packets stay in (FIFO) queue.
>>
>> As we don't have infinite memory, we still can drop packets in enqueue()
>> in case of massive load, but mean of CoDel is to drop packets in
>> dequeue(), using a control law based on two simple parameters :
>>
>> target : target sojourn time (default 5ms)
>> interval : width of moving time window (default 100ms)
>>
>> Selected packets are dropped, unless ECN is enabled and packets can get
>> ECN mark instead.
>>
>> Usage: tc qdisc ... codel [ limit PACKETS ] [ target TIME ]
>>                           [ interval TIME ] [ ecn ]
>>
>> qdisc codel 10: parent 1:1 limit 2000p target 3.0ms interval 60.0ms ecn
>>  Sent 13347099587 bytes 8815805 pkt (dropped 0, overlimits 0 requeues 0)
>>  rate 202365Kbit 16708pps backlog 113550b 75p requeues 0
>>   count 116 lastcount 98 ldelay 4.3ms dropping drop_next 816us
>>   maxpacket 1514 ecn_mark 84399 drop_overlimit 0
>>
>> CoDel must be seen as a base module, and should be used keeping in mind
>> there is still a FIFO queue. So a typical setup will probably need a
>> hierarchy of several qdiscs and packet classifiers to be able to meet
>> whatever constraints a user might have.
>>
>> One possible example would be to use fq_codel, which combines Fair
>> Queueing and CoDel, in replacement of sfq / sfq_red.
>>
>> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>> Signed-off-by: Dave Taht <dave.taht@...ferbloat.net>
>> ---
>> Notes :
>> 1) : Dave Taht will send a nice man-page for this stuff.
>> 2) : the TCA_NETEM_ECN bit is because of include/linux/pkt_sched.h sync
>> with net-next
>>      (I'll send a separate patch for netem)
>>
>
> Applied. Used 3.5 sanitized header (not the one in your patch),
> and fixed whitespace error.
>
>
> Ok, where's the man page :-)
> --
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-- 
Dave Täht
SKYPE: davetaht
US Tel: 1-239-829-5608
http://www.bufferbloat.net
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