HTB Ceil (was: [LARTC] Yet another shaping question)

HTB Ceil (was: [LARTC] Yet another shaping question)

[Peter Rabbitson]

Lately I had time to make some progress on the problem stated at the 
start of this thread. Now however I am facing a problem with HTB not 
working correctly. Since I use the same rules on multiple interfaces, I 
use the same impossibly high ceil for all of them (1Gbyte), and rely on 
priorities in order to distribute traffic. However it does not seem to 
work, although the docs state it should. Here is a minimized example:

root@Arzamas:/etc/init.d# tc -d class show dev wan_a
class htb 1:1 root rate 8000Mbit ceil 8000Mbit burst 1Kb/8 mpu 0b 
overhead 0b cburst 1Kb/8 mpu 0b overhead 0b level 7
class htb 1:80 parent 1:1 prio 0 quantum 1000 rate 40000bit ceil 
8000Mbit burst 1600b/8 mpu 0b overhead 0b cburst 1Kb/8 mpu 0b overhead 
0b level 0
class htb 1:48 parent 1:1 prio 4 quantum 1000 rate 40000bit ceil 
960000bit burst 1600b/8 mpu 0b overhead 0b cburst 1599b/8 mpu 0b 
overhead 0b level 0
class htb 1:58 parent 1:1 prio 6 quantum 1000 rate 40000bit ceil 
1200Kbit burst 1600b/8 mpu 0b overhead 0b cburst 1599b/8 mpu 0b overhead 
0b level 0
root@Arzamas:/etc/init.d#

Traffic flowing into 1:58 is correctly shaped at 150kbytes/s. However 
when traffic starts coming down 1:48 it only gets up to the actual link 
speed less 1:58, which is about 40kbytes/s in my case. If however I cap 
the ceil of the master class to 190kbytes/s - everything works as expected:

root@Arzamas:/etc/init.d# tc -d class show dev wan_a
class htb 1:1 root rate 1520Kbit ceil 1520Kbit burst 1599b/8 mpu 0b 
overhead 0b cburst 1599b/8 mpu 0b overhead 0b level 7
class htb 1:80 parent 1:1 prio 0 quantum 1000 rate 40000bit ceil 
1520Kbit burst 1600b/8 mpu 0b overhead 0b cburst 1599b/8 mpu 0b overhead 
0b level 0
class htb 1:48 parent 1:1 prio 4 quantum 1000 rate 40000bit ceil 
960000bit burst 1600b/8 mpu 0b overhead 0b cburst 1599b/8 mpu 0b 
overhead 0b level 0
class htb 1:58 parent 1:1 prio 6 quantum 1000 rate 40000bit ceil 
1200Kbit burst 1600b/8 mpu 0b overhead 0b cburst 1599b/8 mpu 0b overhead 
0b level 0
root@Arzamas:/etc/init.d#


My question is - how can I shape traffic by priority (deliberately 
allowing starvation), without knowing beforehand the speed of the 
underlying link?

Thank you

Peter
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