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Documentation / networking / gen_stats.txt




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Based on kernel version 3.16. Page generated on 2014-08-06 21:40 EST.

1	Generic networking statistics for netlink users
2	======================================================================
3	
4	Statistic counters are grouped into structs:
5	
6	Struct               TLV type              Description
7	----------------------------------------------------------------------
8	gnet_stats_basic     TCA_STATS_BASIC       Basic statistics
9	gnet_stats_rate_est  TCA_STATS_RATE_EST    Rate estimator
10	gnet_stats_queue     TCA_STATS_QUEUE       Queue statistics
11	none                 TCA_STATS_APP         Application specific
12	
13	
14	Collecting:
15	-----------
16	
17	Declare the statistic structs you need:
18	struct mystruct {
19		struct gnet_stats_basic	bstats;
20		struct gnet_stats_queue	qstats;
21		...
22	};
23	
24	Update statistics:
25	mystruct->tstats.packet++;
26	mystruct->qstats.backlog += skb->pkt_len;
27	
28	
29	Export to userspace (Dump):
30	---------------------------
31	
32	my_dumping_routine(struct sk_buff *skb, ...)
33	{
34		struct gnet_dump dump;
35	
36		if (gnet_stats_start_copy(skb, TCA_STATS2, &mystruct->lock, &dump) < 0)
37			goto rtattr_failure;
38	
39		if (gnet_stats_copy_basic(&dump, &mystruct->bstats) < 0 ||
40		    gnet_stats_copy_queue(&dump, &mystruct->qstats) < 0 ||
41			gnet_stats_copy_app(&dump, &xstats, sizeof(xstats)) < 0)
42			goto rtattr_failure;
43	
44		if (gnet_stats_finish_copy(&dump) < 0)
45			goto rtattr_failure;
46		...
47	}
48	
49	TCA_STATS/TCA_XSTATS backward compatibility:
50	--------------------------------------------
51	
52	Prior users of struct tc_stats and xstats can maintain backward
53	compatibility by calling the compat wrappers to keep providing the
54	existing TLV types.
55	
56	my_dumping_routine(struct sk_buff *skb, ...)
57	{
58	    if (gnet_stats_start_copy_compat(skb, TCA_STATS2, TCA_STATS,
59			TCA_XSTATS, &mystruct->lock, &dump) < 0)
60			goto rtattr_failure;
61		...
62	}
63	
64	A struct tc_stats will be filled out during gnet_stats_copy_* calls
65	and appended to the skb. TCA_XSTATS is provided if gnet_stats_copy_app
66	was called.
67	
68	
69	Locking:
70	--------
71	
72	Locks are taken before writing and released once all statistics have
73	been written. Locks are always released in case of an error. You
74	are responsible for making sure that the lock is initialized.
75	
76	
77	Rate Estimator:
78	--------------
79	
80	0) Prepare an estimator attribute. Most likely this would be in user
81	   space. The value of this TLV should contain a tc_estimator structure.
82	   As usual, such a TLV needs to be 32 bit aligned and therefore the
83	   length needs to be appropriately set, etc. The estimator interval
84	   and ewma log need to be converted to the appropriate values.
85	   tc_estimator.c::tc_setup_estimator() is advisable to be used as the
86	   conversion routine. It does a few clever things. It takes a time
87	   interval in microsecs, a time constant also in microsecs and a struct
88	   tc_estimator to  be populated. The returned tc_estimator can be
89	   transported to the kernel.  Transfer such a structure in a TLV of type
90	   TCA_RATE to your code in the kernel.
91	
92	In the kernel when setting up:
93	1) make sure you have basic stats and rate stats setup first.
94	2) make sure you have initialized stats lock that is used to setup such
95	   stats.
96	3) Now initialize a new estimator:
97	
98	   int ret = gen_new_estimator(my_basicstats,my_rate_est_stats,
99	       mystats_lock, attr_with_tcestimator_struct);
100	
101	   if ret == 0
102	       success
103	   else
104	       failed
105	
106	From now on, every time you dump my_rate_est_stats it will contain
107	up-to-date info.
108	
109	Once you are done, call gen_kill_estimator(my_basicstats,
110	my_rate_est_stats) Make sure that my_basicstats and my_rate_est_stats
111	are still valid (i.e still exist) at the time of making this call.
112	
113	
114	Authors:
115	--------
116	Thomas Graf <tgraf@suug.ch>
117	Jamal Hadi Salim <hadi@cyberus.ca>
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