LARTC - Jun 2006 - why can not turn the bandwidth knob up to 100Mbit

I am using the script below to simulate a very high bandwidth connection.I find
that I could not turn the bandwidth knob up to 100Mbit.I have had a look at this
generally,but could not find an answer.any help would much appreciated as i have
spent a lot of time on this and have not found any answers anywhere.
In my test,I have four network cards and their rate are all 1000Mbps.
  my scripts:
          DEV="eth1" 
 tc qdisc add dev $DEV root handle 1: htb default 24 
 tc class add dev $DEV parent 1: classid 1:1 htb rate 500Mbit ceil 500Mbit prio
0
 
 tc class add dev $DEV parent 1:1 classid 1:11 htb rate 100Mbit ceil 100Mbit
prio 1
 tc class add dev $DEV parent 1:1 classid 1:12 htb rate 100Mbit ceil 100Mbit
prio 2
 
 tc class add dev $DEV parent 1: classid 1:2 htb rate 500Mbit prio 3 
 
 tc class add dev $DEV parent 1:2 classid 1:21 htb rate 150Mbit ceil 150Mbit
prio 4
 
 tc class add dev $DEV parent 1:2 classid 1:22 htb rate 100Mbit ceil 100Mbit
prio 5
  
 tc class add dev $DEV parent 1:2 classid 1:23 htb rate 100Mbit ceil 100Mbit
prio 6
 
 tc class add dev $DEV parent 1:2 classid 1:24 htb rate 100Mbit ceil 100Mbit
prio 7
 
 
 tc qdisc add dev $DEV parent 1:11 handle 111: sfq perturb 5 
 tc qdisc add dev $DEV parent 1:12 handle 112: sfq perturb 5 
 tc qdisc add dev $DEV parent 1:21 handle 121: sfq perturb 10 
 tc qdisc add dev $DEV parent 1:22 handle 122: sfq perturb 10 
 tc qdisc add dev $DEV parent 1:23 handle 133: sfq perturb 10 
 tc qdisc add dev $DEV parent 1:24 handle 124: sfq perturb 10 
 
 
 tc filter add dev $DEV parent 1:0 protocol ip prio 1 handle 1 fw classid 1:11 
 tc filter add dev $DEV parent 1:0 protocol ip prio 2 handle 2 fw classid 1:12 
 tc filter add dev $DEV parent 1:0 protocol ip prio 3 handle 3 fw classid 1:21 
 tc filter add dev $DEV parent 1:0 protocol ip prio 4 handle 4 fw classid 1:22 
 tc filter add dev $DEV parent 1:0 protocol ip prio 5 handle 5 fw classid 1:23 
 tc filter add dev $DEV parent 1:0 protocol ip prio 6 handle 6 fw classid 1:24 
  (using "tc -s class show dev eth1" to list result,if the rate of
class 1:21 is 100Mbit,the result is between 99M and 100M;
if the rate of class 1:21 is 150Mbit ,the result is between 45M and 50M;)
  Thank you and regards.
Xin Mingting 


 		
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> (using "tc -s class show dev eth1" to list result,if the rate of
class 1:21
> is 100Mbit,the result is between 99M and 100M;
> if the rate of class 1:21 is 150Mbit ,the result is between 45M and 50M;)
I wonder if this has something to do with what devik writes on the htb homepage:

<qoute>
Limitation: when you operate with high rates on computer with low
resolution timer you need some minimal burst and cburst to be set for
all classes. Timer resolution on i386 systems is 10ms and 1ms on
Alphas. The minimal burst can be computed as
max_rate*timer_resolution. So that for 10Mbit on plain i386 you needs
burst 12kb.

If you set too small burst you will encounter smaller rate than you
set. Latest tc tool will compute and set the smallest possible burst
when it is not specified.
</quote>