Documentation/networking/gen_stats.txt

   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 nees 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, everytime you dump my_rate_est_stats it will contain
 107 uptodate 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>