关于tc 中htb算法中的r2q和quantum的做用

tc qdisc add dev eth0 root handle 1: htb r2q 10 default 10

r2q：在规则中的作用是用来分配剩余带宽的全局变量，它的默认值为10，此时最实用的规则的速度为15KBps（120kbit）。

quantum与r2q的关系为quantum=rate/r2q，quantum的值必须在1500到60000之间，值越小越好

每个规则的quantum的值就是从父类借用带宽的因子（也就是每个子类每次可以从父类借用空闲带宽的大小）也可以说是与其他子类同时从父类借带宽的比例。

rate单位为Mbit时，上限临界值为 0.7左右，即r2q最小要设为0.7。rate单位为Gbit时，上限临界值为700左右，即r2q最小要设为700。

tc returns: "quantum of class # is small. Consider r2q change."

1. Vulpes 
2. Bugs 
3. Bug #322180

Reported by Alwin Garside  on 2009-01-28 2AffectsStatusImportanceAssigned toMilestone? Vulpes Triaged 中国学网 www.xue163.com

Low Alwin Garside Also affects project (?)  Also affects distribution/package  Nominate for series

Bug Description

It is documented in HTB manual. The complaint was not displayed before and sharing was silently wrong. Quantum of leaf should be between 1500 and 60000 and it is computed as rate/r2q (or can be supplied independly). So that if your maximal leaf rate is 1Mbit (120000Bps) then r2q should be 3. If max rate is 10kbit (1200Bps) then r2q should be 1. It is warning only and will not affect functionality, only precision. devik

Smallest rate : 16kbit = 2 kilobyt / r2q (=10) = 200. And this is < 1500. So you get warnings. Biggest rate : 100mbit = 12.5 mbyte / r2q = 1.2 Mbyte > 60.000. So you get warnings.

If you do tc qdisc add dev eth0 root handle 1: htb default 10 r2q 1 Smallest rate : 16kbit = 2kilobyte / r2k = 2000. And this is > 1500. So no warnings. Biggest rate : 100mbit = 12.5 mbyte / r2q = 12.5 Mbyte > 60.000. So you get warnings. But you can overrule the quantum : tc class add dev eth0 parent 1:1 classid 1:11 htb rate 128kbit burst 2k quantum 60000

Quantum is used when 2 classes are getting more bandwidth then the rate. So it's only important for sharing the remaining bandwidth. In that case, each class may send quantum bytes.

see: http://archives.free.net.ph/message/20051020.143239.c839805b.en.html#lartc

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tc qdisc add dev eth0 root handle 1: htb r2q 10 default 10

r2q：在规则中的作用是用来分配剩余带宽的全局变量，它的默认值为10，此时最实用的规则的速度为15KBps（120kbit）。
quantum与r2q的关系为quantum=rate/r2q，quantum的值必须在1500到60000之间，值越小越好
每个规则的quantum的值就是从父类借用带宽的因子（也就是每个子类每次可以从父类借用空闲带宽的大小）也可以说是与其他子类同时从父类借带宽的比例。

TC HTB r2q

HTB:
quantum of class 10001 is big. Consider r2q change.

根据HTB的官方文档显示，quantum是在可以“借”的情况下，一次可以“借”多少，并且说这个值最好尽量的小，但要大于MTU；而且这个值是不用手动设置，它会根据r2q的值计算出来。


Changing burst will not remove the warning.  r2q is "rate to quantum" is used

to calculate the quantum for each class : quantum = rate / r2q.  Quantum must

be 1500 < quantum < 60000.  Otherwise you will get warnings from the kernel.

Solution : choose r2q so for each class 1500 < quantum < 60000

Or choose the best r2q you can and specify the quantum manually if you add a

class.



> tc qdisc add dev eth0 root handle 1: htb default 10

Default r2q = 10.



> tc class add dev eth0 parent 1: classid 1:1 htb rate 100mbit burst 2k

> tc class add dev eth0 parent 1:1 classid 1:10 htb rate 80mbit ceil 100mbit

> burst 2k

>

> tc class add dev eth0 parent 1:1 classid 1:11 htb rate 128kbit burst 2k

> tc class add dev eth0 parent 1:11 classid 1:21 htb rate 16kbit ceil 56kbit

> burst 2k

> tc class add dev eth0 parent 1:11 classid 1:22 htb rate 16kbit ceil 40kbit

> burst 2k

> tc class add dev eth0 parent 1:11 classid 1:23 htb rate 16kbit ceil 72kbit

> burst 2k

> tc class add dev eth0 parent 1:11 classid 1:24 htb rate 16kbit ceil 64kbit

> burst 2k

> tc class add dev eth0 parent 1:11 classid 1:25 htb rate 16kbit ceil 40kbit

> burst 2k

> tc class add dev eth0 parent 1:11 classid 1:26 htb rate 16kbit ceil 40kbit

> burst 2k

> tc class add dev eth0 parent 1:11 classid 1:27 htb rate 16kbit ceil 32kbit

> burst 2k

> tc class add dev eth0 parent 1:11 classid 1:28 htb rate 16kbit ceil 56kbit

> burst 2k

Smallest rate : 16kbit = 2 kilobyt / r2q (=10) = 200.  And this is < 1500.  So

you get warnings.

Biggest rate : 100mbit = 12.5 mbyte / r2q = 1.2 Mbyte > 60.000.  So you get

warnings. 



If you do

tc qdisc add dev eth0 root handle 1: htb default 10 r2q 1

Smallest rate : 16kbit = 2kilobyte / r2k = 2000.  And this is > 1500.  So no

warnings.

Biggest rate : 100mbit = 12.5 mbyte / r2q = 12.5 Mbyte > 60.000.  So you get

warnings.  But you can overrule the quantum :

tc class add dev eth0 parent 1:1 classid 1:11 htb rate 128kbit burst 2k

quantum 60000



Quantum is used when 2 classes are getting more bandwidth then the rate.   So

it‘s only important for sharing the remaining bandwidth.  In that case, each

class may send quantum bytes.

TC HTB r2q