A HTB problem

["Yong Yao (yoyao)" <yoyao@xxxxxxxxx>]

My hardware is a Linksys AP with MIPS 300MHz and Linux kernel 2.4.20.

The traffics are from two LAN switch ports to WAN port. And the traffics are generate at a rate of 80Mbit. So the total traffic to WAN port is 160Mbit. The shaping works well that the traffic to WAN port is about 50/30Mbit according to configuration. But the priority seems strange when the root rate is 50Mbit.

When the root ceil is 50Mb and ceil for class 12 and 13 is 50Mb, the actual throughput for class 12 and 13 are 32Mb and 16Mb. But in theory, class 12 can almost occupy all the 50Mb throughput for it has a higher priority.

When the root ceil is 30Mb and ceil for class 12 and 13 is 30Mb, HTB works welll that class 12 almost occupies all the 30Mb throughput.

The output for tc qdisc show is like the following:

qdisc pfifo 140: dev vlan2 limit 10p
qdisc pfifo 130: dev vlan2 limit 80p
qdisc pfifo 120: dev vlan2 limit 80p
qdisc pfifo 110: dev vlan2 limit 10p
qdisc htb 1: dev vlan2 r2q 10 default 13 direct_packets_stat 0

The output for tc -d -s class show dev vlan2 is like the following for root rate is 50Mbit and ceil for class is 50Mbit:

class htb 1:11 parent 1:1 leaf 110: prio 0 quantum 37500 rate 3000Kbit ceil 10000Kbit burst 50Kb/8 mpu 0b overhead 0b cburst 14098b  Sent 0 bytes 0 pkts (dropped 0, overlimits 0)
 lended: 0 borrowed: 0 giants: 0
 tokens: 111847 ctokens: 9240

class htb 1:1 root rate 50000Kbit ceil 50000Kbit burst 64093b/8 mpu 0b overhead 0b cburst 64093b/8 mpu 0b overhead 0b level 7  Sent 574199301 bytes 563132 pkts (dropped 0, overlimits 0)  rate 48914Kbit 5996pps
 lended: 556777 borrowed: 0 giants: 0
 tokens: -8491 ctokens: -8491

class htb 1:13 parent 1:1 leaf 130: prio 5 quantum 1000 rate 50000bit ceil 50000Kbit burst 10Kb/8 mpu 0b overhead 0b cburst 64093b/  Sent 194194097 bytes 190578 pkts (dropped 671278, overlimits 0)  rate 16780Kbit 2058pps backlog 81p
 lended: 571 borrowed: 189926 giants: 0
 tokens: -1018474 ctokens: 2725

class htb 1:12 parent 1:1 leaf 120: prio 1 quantum 6250 rate 500000bit ceil 50000Kbit burst 100Kb/8 mpu 0b overhead 0b cburst 64093  Sent 380296800 bytes 372840 pkts (dropped 502882, overlimits 0)  rate 32212Kbit 3947pps backlog 81p
 lended: 5784 borrowed: 366975 giants: 0
 tokens: -753535 ctokens: -2291

class htb 1:14 parent 1:1 leaf 140: prio 7 quantum 1000 rate 12000bit ceil 50000Kbit burst 80Kb/8 mpu 0b overhead 0b cburst 64093b/  Sent 0 bytes 0 pkts (dropped 0, overlimits 0)
 lended: 0 borrowed: 0 giants: 0
 tokens: 44739242 ctokens: 8401

The output for tc -d -s class show dev vlan2 is like the following for root rate is 30Mbit and ceil for class is 30Mbit:

class htb 1:11 parent 1:1 leaf 110: prio 0 quantum 37500 rate 3000Kbit ceil 10000Kbit burst 50Kb/8 mpu 0b overhead 0b cburst 14098b  Sent 0 bytes 0 pkts (dropped 0, overlimits 0)
 lended: 0 borrowed: 0 giants: 0
 tokens: 111847 ctokens: 9240

class htb 1:1 root rate 30000Kbit ceil 30000Kbit burst 39090b/8 mpu 0b overhead 0b cburst 39090b/8 mpu 0b overhead 0b level 7  Sent 499116401 bytes 489356 pkts (dropped 0, overlimits 0)  rate 28831Kbit 3533pps
 lended: 480785 borrowed: 0 giants: 0
 tokens: -8619 ctokens: -8619

class htb 1:13 parent 1:1 leaf 130: prio 5 quantum 1000 rate 50000bit ceil 30000Kbit burst 10Kb/8 mpu 0b overhead 0b cburst 39090b/  Sent 47379739 bytes 46477 pkts (dropped 1342031, overlimits 0)  rate 178992bit 22pps backlog 81p
 lended: 846 borrowed: 45549 giants: 0
 tokens: -513805 ctokens: 1247

class htb 1:12 parent 1:1 leaf 120: prio 1 quantum 6250 rate 500000bit ceil 30000Kbit burst 100Kb/8 mpu 0b overhead 0b cburst 39090  Sent 451978320 bytes 443116 pkts (dropped 710651, overlimits 0)  rate 28672Kbit 3513pps backlog 81p
 lended: 7725 borrowed: 435310 giants: 0
 tokens: -344531 ctokens: -8589

class htb 1:14 parent 1:1 leaf 140: prio 7 quantum 1000 rate 12000bit ceil 30000Kbit burst 80Kb/8 mpu 0b overhead 0b cburst 39090b/  Sent 0 bytes 0 pkts (dropped 0, overlimits 0)
 lended: 0 borrowed: 0 giants: 0
 tokens: 44739242 ctokens: 8540

 

Yong Yao
Software Engineer

Cisco CRDC Linksys
Floor 11-16, Block C,
No.900, Yishan Road,
Caohejing Hi-Tech Park
Shanghai, P.R.C.200233

yoyao@xxxxxxxxx

tel:	+86(21)24057124

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