Date:	Fri, 23 Dec 2011 02:08:54 -0500
From:	"John A. Sullivan III" <jsullivan@...nsourcedevel.com>
To:	Dave Taht <dave.taht@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: SFQ on HFSC leaf does not seem to work

On Fri, 2011-12-23 at 01:40 -0500, John A. Sullivan III wrote:
> On Fri, 2011-12-23 at 07:32 +0100, Dave Taht wrote:
> > On Fri, Dec 23, 2011 at 7:00 AM, John A. Sullivan III
> > <jsullivan@...nsourcedevel.com> wrote:
> > > Hello, all.  I have an experimental HFSC setup with three leaf classes
> > > each with SFQ as the final qdisc.  One queue is for ssh on port 822, one
> > > is for tcp traffic on port 443, the third is the default.
> > >
> > > If I flood the 443 queue with netcat, my ssh sessions are responsive and
> > > my continuous ping shows a round trip time of around 50ms in keeping
> > > with my netem settings.
> > >
> > > However, if I flood the default queue with netcat on port 80, ssh is
> > > still responsive but my ping round trip times shoot up over 3000ms.
> > >
> > > I thought it might be the bufferbloat phenomenon so I reduced the
> > > txqueuelen on both sides of the ping to 0.  Both sides use old 10BaseT
> > > NICs and have no ring buffer.  I also set the SFQ limit on the default
> > > queue to 2 just in case.  Still no difference.
> > 
> > Your txqueuelen on the ifb devices is probably 1000.
> Alas, not.  They defaulted to 32 and I reset them to 0 :(
> 
> I'll also paste in a slightly optimized rule set but it still made no
> difference.
> > 
> > 
> > 
> > >
> > > The default queue is dequeuing at roughly 400 kbits which matches my
> > > HFSC configuration.  A full sized packet should take 30 ms to pass at
> > > that rate ((1514 * 8)/400,000) so, if I am round robining the queues, I
> > > would expect latency on a default sized ping to be only 30 ms plus the
> > > netem delay.
> > >
> > > Where might this 3000 ms delay be coming from?
> > >
> > > Here is the rule set:
> > >
> > #!/bin/sh
> 
> tc qdisc add dev eth1 root handle 1: hfsc default 20
> tc class add dev eth1 parent 1: classid 1:1 hfsc sc rate 1490kbit ul rate 1490kbit
> tc class add dev eth1 parent 1:1 classid 1:20 hfsc rt rate 400kbit ls rate 200kbit
> tc qdisc add dev eth1 parent 1:20 handle 1201 sfq perturb 10
> tc class add dev eth1 parent 1:1 classid 1:10 hfsc rt umax 16kbit dmax 50ms rate 200kbit ls rate 1000kbit
> tc qdisc add dev eth1 parent 1:10 handle 1101 sfq perturb 60
> tc class add dev eth1 parent 1:1 classid 1:30 hfsc rt umax 1514b dmax 20ms rate 20kbit
> tc qdisc add dev eth1 parent 1:30 handle 1301 sfq perturb 60
> iptables -t mangle -A POSTROUTING -p 6 --syn --dport 443 -j CONNMARK --set-mark 0x10
> iptables -t mangle -A PREROUTING -p 6 --syn --dport 822 -j CONNMARK --set-mark 0x11
> iptables -t mangle -A POSTROUTING -o eth1 -p 6 -j CONNMARK --restore-mark
> modprobe ifb
> ifconfig ifb0 up
> ifconfig ifb1 up
> tc qdisc add dev ifb0 root handle 1: hfsc default 20
> tc class add dev ifb0 parent 1: classid 1:1 hfsc sc rate 1490kbit ul rate 1490kbit
> tc class add dev ifb0 parent 1:1 classid 1:20 hfsc rt rate 400kbit ls rate 200kbit
> tc qdisc add dev ifb0 parent 1:20 handle 1201 netem delay 25ms 5ms distribution normal loss 0.1% 30%
> tc class add dev ifb0 parent 1:1 classid 1:10 hfsc rt umax 16kbit dmax 50ms rate 200kbit ls rate 1000kbit
> tc qdisc add dev ifb0 parent 1:10 handle 1101 netem delay 25ms 5ms distribution normal loss 0.1% 30%
> tc class add dev ifb0 parent 1:1 classid 1:30 hfsc rt umax 1514b dmax 20ms rate 20kbit
> tc qdisc add dev ifb0 parent 1:30 handle 1301 netem delay 25ms 5ms distribution normal loss 0.1% 30%
> tc filter add dev ifb0 parent 1:0 protocol ip prio 1 handle 6: u32 divisor 1
> tc filter add dev ifb0 parent 1:0 protocol ip prio 1 u32 match ip protocol 6 0xff link 6: offset at 0 mask 0x0f00 shift 6 plus 0 eat
> tc filter add dev ifb0 parent 1:0 protocol ip prio 1 u32 ht 6:0 match tcp src 443 0x00ff flowid 1:10
> tc filter add dev ifb0 parent 1:0 protocol ip prio 1 u32 ht 6:0 match tcp dst 822 0xff00 flowid 1:30
> tc qdisc add dev ifb1 root handle 2 netem delay 25ms 5ms distribution normal loss 0.1% 30%
> tc qdisc add dev eth1 ingress
> tc filter add dev eth1 parent ffff: protocol ip prio 50 u32 match u32 0 0 action mirred egress redirect dev ifb0
> tc filter add dev eth1 parent 1:1 protocol ip prio 1 handle 0x11 fw flowid 1:30
> tc filter add dev eth1 parent 1:1 protocol ip prio 1 handle 0x10 fw flowid 1:10
> tc filter add dev eth1 parent 1:1 protocol ip prio 2 u32 match u32 0 0 flowid 1:20
> tc filter add dev eth1 parent 1:0 protocol ip prio 1 u32 match u32 0 0 flowid 1:1 action mirred egress redirect dev ifb1
<snip>
I just tried setting the txqueuelen to 5 instead of 0 as per Dave's
offlist recommendation but it made no difference.  When I start the bulk
traffic, the ICMP response time builds over about 10s from 60ms to
3100ms.  Any ideas where it is coming from? Thanks - John

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