请教Linux内核qos tbf令牌桶算法原理

lli_njupt

因为需要扩展tbf以实现一些特殊的功能，但是发现很难看明白sch_tbf.c中的算法解释，另外搜索了一下相关资料，
都是说一些tbf基本原理，剩下的都是英文的资料，研究了半天，就是找不到头绪，希望了解算法的高人不吝赐教。

1. 
   
2. from sch_tbf.c
   
3. 
   
4. /*        Simple Token Bucket Filter.
   
5.         =======================================
   
6. 
   
7.         SOURCE.
   
8.         -------
   
9. 
   
10.         None.
    
11. 
    
12.         Description.
    
13.         ------------
    
14. 
    
15.         A data flow obeys TBF with rate R and depth B, if for any
    
16.         time interval t_i...t_f the number of transmitted bits
    
17.         does not exceed B + R*(t_f-t_i).
    
18. 
    
19.         Packetized version of this definition:
    
20.         The sequence of packets of sizes s_i served at moments t_i
    
21.         obeys TBF, if for any i<=k:
    
22. 
    
23.         s_i+....+s_k <= B + R*(t_k - t_i)
    
24. 
    
25.         Algorithm.
    
26.         ----------
    
27. 
    
28.         Let N(t_i) be B/R initially and N(t) grow continuously with time as:
    
29. 
    
30.         N(t+delta) = min{B/R, N(t) + delta}
    
31. 
    
32.         If the first packet in queue has length S, it may be
    
33.         transmitted only at the time t_* when S/R <= N(t_*),
    
34.         and in this case N(t) jumps:
    
35. 
    
36.         N(t_* + 0) = N(t_* - 0) - S/R.
    
37. 
    
38. 
    
39. 
    
40.         Actually, QoS requires two TBF to be applied to a data stream.
    
41.         One of them controls steady state burst size, another
    
42.         one with rate P (peak rate) and depth M (equal to link MTU)
    
43.         limits bursts at a smaller time scale.
    
44. 
    
45.         It is easy to see that P>R, and B>M. If P is infinity, this double
    
46.         TBF is equivalent to a single one.
    
47. 
    
48.         When TBF works in reshaping mode, latency is estimated as:
    
49. 
    
50.         lat = max ((L-B)/R, (L-M)/P)
    
51. 
    
52. 
    
53.         NOTES.
    
54.         ------
    
55. 
    
56.         If TBF throttles, it starts a watchdog timer, which will wake it up
    
57.         when it is ready to transmit.
    
58.         Note that the minimal timer resolution is 1/HZ.
    
59.         If no new packets arrive during this period,
    
60.         or if the device is not awaken by EOI for some previous packet,
    
61.         TBF can stop its activity for 1/HZ.
    
62. 
    
63. 
    
64.         This means, that with depth B, the maximal rate is
    
65. 
    
66.         R_crit = B*HZ
    
67. 
    
68.         F.e. for 10Mbit ethernet and HZ=100 the minimal allowed B is ~10Kbytes.
    
69. 
    
70.         Note that the peak rate TBF is much more tough: with MTU 1500
    
71.         P_crit = 150Kbytes/sec. So, if you need greater peak
    
72.         rates, use alpha with HZ=1000 :-)
    
73. 
    
74.         With classful TBF, limit is just kept for backwards compatibility.
    
75.         It is passed to the default bfifo qdisc - if the inner qdisc is
    
76.         changed the limit is not effective anymore.
    
77. */
    

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lli_njupt

自己顶，没人知道？还是...

tjushengyao

楼主求救啊   请问你有令牌桶算法的源代码吗？