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
[off-list ref] wrote:

quoted

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.

quoted

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

quoted

Thanks - John

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