Re: [LARTC] sfq, queue len and dropped packets

[don-lartc@isis.cs3-inc.com (Don Cohen)]

  On Wednesday 10 April 2002 17:26, Mihai RUSU wrote:
  > If I use sfq qdisc on a CBQ class I get a lot of dropped packets and the
  > backlog itr almost always to its full value: 128. From the HOWTO I
  > understand that the queue is at 128 packets, and SFQ shows 128/1024 flows
  > , but how can I increase that value ? I have tried ip link set txqueuelen
  > but this only increases the tx queue on the interface.
First, are you sure you're not under attack?
If you are running a small network this seems implausible.
Also, the constant high backlog probably indicates that you're
just getting input faster than you can forward it.  In that case
increasing the queue length won't result in many fewer drops.
It will just increase average delay.

  > qdisc sfq d468: quantum 1514b limit 128p flows 128/1024 perturb 10sec
  >  Sent 373321530 bytes 477032 pkts (dropped 120119, overlimits 0)
  >  backlog 120p
  >
  > How can I increase that 128p limit ?
  You can find it on www.docum.org under FAQ.
  You need to change the kernel source to do so.
This tells how to decrease, not increase the limit (and the
explanation of why you'd want to makes no sense to me).
In order to increase the limit you have to not only increase
the queue "depth", but also change a type declaration, something
like sfq_index - from char to int.  There's a comment about that
in the code.
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