Re: [LARTC] Why did I need strange ceiling settings?

[Andy Furniss <lists@andyfurniss.entadsl.com>]

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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