Re: [LARTC] HTB rate miscalculation

[Andy Furniss <andy.furniss@dsl.pipex.com>]

Marcus Felipe Pereira wrote:
> Hi,
>  I've migrated my tc configuration from CBQ to HTB.
> 
>  One problem appeared. Htb seems to miscalculate the bandwidth for 
> classes with greater rates.
>  For rates below 2Mbit there is almost no difference between the 
> configured and the measured rate.
> 
>  For large ones the problem starts. My root class has 10Mbit rate and 
> when the interface has heavy trafic the measured bandwidth coudn't get 
> more then 8.5Mbit.
> 
>   "# tc -s class show ...." shows that the root class has about the 
> 10Mbit, but the link stats shows mutch less.
> 
>  The solution was to put the htb ceil on about 12Mbit. Then I can get to 
> the 10Mbit. When using CBQ I didn't have this problem.
> 
>  Is there any parameter that I can change to correct the rate calculation?
>  Any one has similar problem?

What counters are you using to measure?

Does it do the same if you test with a single tcp stream and a very 
simple setup like -

tc qdisc add dev eth0 root handle 1:0 htb
tc class add dev eth0 parent 1:0 classid 1:1 htb rate 10mbit
tc filter add dev eth0 parent 1:0 protocol ip u32 match u32 0 0 flowid 1:1

Andy.
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