linux/Documentation/networking/gen_stats.txt
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   1Generic networking statistics for netlink users
   2======================================================================
   3
   4Statistic counters are grouped into structs:
   5
   6Struct               TLV type              Description
   7----------------------------------------------------------------------
   8gnet_stats_basic     TCA_STATS_BASIC       Basic statistics
   9gnet_stats_rate_est  TCA_STATS_RATE_EST    Rate estimator
  10gnet_stats_queue     TCA_STATS_QUEUE       Queue statistics
  11none                 TCA_STATS_APP         Application specific
  12
  13
  14Collecting:
  15-----------
  16
  17Declare the statistic structs you need:
  18struct mystruct {
  19        struct gnet_stats_basic bstats;
  20        struct gnet_stats_queue qstats;
  21        ...
  22};
  23
  24Update statistics:
  25mystruct->tstats.packet++;
  26mystruct->qstats.backlog += skb->pkt_len;
  27
  28
  29Export to userspace (Dump):
  30---------------------------
  31
  32my_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
  49TCA_STATS/TCA_XSTATS backward compatibility:
  50--------------------------------------------
  51
  52Prior users of struct tc_stats and xstats can maintain backward
  53compatibility by calling the compat wrappers to keep providing the
  54existing TLV types.
  55
  56my_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
  64A struct tc_stats will be filled out during gnet_stats_copy_* calls
  65and appended to the skb. TCA_XSTATS is provided if gnet_stats_copy_app
  66was called.
  67
  68
  69Locking:
  70--------
  71
  72Locks are taken before writing and released once all statistics have
  73been written. Locks are always released in case of an error. You
  74are responsible for making sure that the lock is initialized.
  75
  76
  77Rate Estimator:
  78--------------
  79
  800) 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
  92In the kernel when setting up:
  931) make sure you have basic stats and rate stats setup first.
  942) make sure you have initialized stats lock that is used to setup such
  95   stats.
  963) 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
 106From now on, every time you dump my_rate_est_stats it will contain
 107up-to-date info.
 108
 109Once you are done, call gen_kill_estimator(my_basicstats,
 110my_rate_est_stats) Make sure that my_basicstats and my_rate_est_stats
 111are still valid (i.e still exist) at the time of making this call.
 112
 113
 114Authors:
 115--------
 116Thomas Graf <tgraf@suug.ch>
 117Jamal Hadi Salim <hadi@cyberus.ca>
 118
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