Re: Why did I need strange ceiling settings?

Linux Advanced Routing and Traffic Control

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Philipp Leusmann wrote:
Hi all,

I recently installed traffic shaping on my ADSL line with a nominal upload
rate of 1MBit. My Modem says it has an upload bitrate of 843 kbits.
So I thought, to use a ceiling of 800kbit for the root qdisc is a good idea.
But with that setting I only achieved upload rates of around 300kbits
whereas I reached around 650 kbits without traffic shaping.
Yesterday I played a little with the ceiling value and found that increasing
it to 175kBps did the job.
Could anybody please explain this strange behaviour?
My shaping script looks as follows:

I see nothing :-)

DSL usually uses atm and the showtime rate of your modem is at this level. (FWIW 843kbit is not a valid DSL rate (multiple of 32kbit).

You can patch (may be mainline eventually) kernel/tc to do atm rates in which case you can set egress rate close to showtime rate. Without this 80% or less will be needed (depends on traffic packet size).

As for other wierdness - could be that htb/hfsc sometimes choose lame defaults (3/1 IIRC) for queue length on interfaces with low/0 default Q len - ppp/vlan/br etc. So add some qdiscs to leaf classes so you can choose your own lengths.

Andy.
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