Re: [LARTC] Low latency on large uploads - almost done but not quite.

[Stef Coene <stef.coene@docum.org>]

On Sunday 15 June 2003 13:44, Thilo Schulz wrote:
> On Sunday 15 June 2003 11:09, you wrote:
> > > Here's still my script, if you are interested to look at it.
> >
> > I'm interested and I have some remarks.
> >
> > Your burst is too low.  I understand you want a minimum burst, but you
> > have to follow some rules.  The best you can do is to remove the
> > burst/cburst option so htb can calculate the minimum burst/cburst for
> > you.
>
> yes, sounds reasonable now that I spend a second thought about it.
>
> > And don't you get quantum errors in your kernel log?  That's because your
> > quantum is too low for the classes.  There is a long explanation for
> > this, see www.docum.org on the faq page.
>
> hmm .. quantum? I have never set quantum with any parameter, or have I?
No.  Quantum is used for leaf classes to determine the amount of packets they 
can send.  It's calculates as rate / r2q.  And r2q is 10 by default.  You can 
overrule r2q if you add the htb qdisc and you can overrule quantum if you add 
a htb class.  Quantum must be > 1500 (the size of 1 packet) and < 60000.  

> > You also use different prio's.  This can be ok in most cases, except if
> > you have a low prio class that's sending more data then the configured
> > rate. If you do so, the latency can go up for that class.  I (still)
> > didn't test it myself, but you can find prove of it on the htb homepage. 
> > The solution for this is to make sure you never put too much traffic in a
> > low prio class.
>
> I have given plenty of bandwidth to the 1:10 class. Quake3 streams are max.
> 1500 bytes/s. And ssh does not use that much either.
Ok.  As long as you are aware of the problem.  You can also try to limit the 
amount of packets the filters with a policer.  So there are never too much 
packets in a class.

> > > # now make all qdiscs simple pfifo
> > > # small queues for minimum latency
> > > tc qdisc add dev $DEV parent 1:10 handle 20: pfifo limit 0
> > > tc qdisc add dev $DEV parent 1:11 handle 30: pfifo limit 0
> >
> > Are you sure limit 0 is possible ????
>
> Yes, at least the status command showed me, that the limit was set to 0.
Ok.

Stef

-- 

stef.coene@docum.org
 "Using Linux as bandwidth manager"
     http://www.docum.org/
     #lartc @ irc.oftc.net

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