netdev - RE: Can I limit the number of active tx per TCP socket?

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Message-ID: <1394202127.20149.14.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Fri, 07 Mar 2014 06:22:07 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	'Neal Cardwell' <ncardwell@...gle.com>,
	Rick Jones <rick.jones2@...com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: Can I limit the number of active tx per TCP socket?

On Fri, 2014-03-07 at 12:29 +0000, David Laight wrote:

> I'll probably look at delaying the sends within our own code.

That would be bad.

Just use fq/pacing, this is way better. Its designed for this usage.

trick is to reduce 'quantum' as you mtu is 273+14 bytes.

QUANTUM=$((273+14))
tc qdisc replace dev eth0 root fq quantum $QUANTUM initial_quantum $QUANTUM

This will _perfectly_ pace packets every 34 ms.

If you share your ethernet device with this 64k destination, and other
uses, then you need a more complex setup with HTB plus two classes, and
fq running at the htb leaf

DEV=eth0

MTU=273
QUANTUM=$(($MTU+14))
DESTINATION=10.246.11.52/32   # change this to meet the network/host

tc qdisc del dev $DEV root &> /dev/null

tc qdisc add dev $DEV handle 1: root htb default 1

tc class add dev $DEV parent 1: classid 1:1 htb rate 1Gbit
tc class add dev $DEV parent 1: classid 1:2 htb rate 64kbit

tc filter add dev $DEV protocol ip parent 1:0 prio 1 u32 match ip dst $DESTINATION flowid 1:2

tc qdisc add dev $DEV parent 1:1 est 1sec 4sec fq
tc qdisc add dev $DEV parent 1:2 est 1sec 4sec fq quantum $QUANTUM initial_quantum $QUANTUM




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