netdev - large divisor for flow classifier

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Date:	Fri, 15 Oct 2010 14:14:15 -0400
From:	Jonathan Thibault <jonathan@...igue.com>
To:	Patrick McHardy <kaber@...sh.net>
CC:	netdev@...r.kernel.org
Subject: large divisor for flow classifier

 It appears that when setting a fairly large divisor on the flow classifier for sfq, traffic stops altogether.

On my machine, anything above divisor 2200 seems to stop all traffic.  If I want to be fair between hosts (but not flows) for a large network (say 6000 hosts), I run into problems.  Obviously the rates here are quite low but this is just an example.

I also tested on a real interface with the same results.

Example that works:

tc qdisc add dev ifb0 root handle 3: htb default 10
  tc class add dev ifb0 parent 3: classid 3:1 htb rate 80kbit
    tc class add dev ifb0 parent 3:1 classid 3:10 htb rate 80kbit
      tc qdisc add dev ifb0 parent 3:10 handle 310: sfq perturb 10
      tc filter add dev ifb0 parent 3: protocol all prio 1 u32 match mark 0x000 0xf00 flowid 3:10
      tc filter add dev ifb0 parent 310: protocol all handle 0x310 flow hash keys dst divisor 1024

Example that doesn't work:

tc qdisc add dev ifb0 root handle 3: htb default 10
  tc class add dev ifb0 parent 3: classid 3:1 htb rate 80kbit
    tc class add dev ifb0 parent 3:1 classid 3:10 htb rate 80kbit
      tc qdisc add dev ifb0 parent 3:10 handle 310: sfq perturb 10
      tc filter add dev ifb0 parent 3: protocol all prio 1 u32 match mark 0x000 0xf00 flowid 3:10
      tc filter add dev ifb0 parent 310: protocol all handle 0x310 flow hash keys dst divisor 6144

Jonathan
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