gen_stats.rst 3.9 KB

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  1. .. SPDX-License-Identifier: GPL-2.0
  2. ===============================================
  3. Generic networking statistics for netlink users
  4. ===============================================
  5. Statistic counters are grouped into structs:
  6. ==================== ===================== =====================
  7. Struct TLV type Description
  8. ==================== ===================== =====================
  9. gnet_stats_basic TCA_STATS_BASIC Basic statistics
  10. gnet_stats_rate_est TCA_STATS_RATE_EST Rate estimator
  11. gnet_stats_queue TCA_STATS_QUEUE Queue statistics
  12. none TCA_STATS_APP Application specific
  13. ==================== ===================== =====================
  14. Collecting:
  15. -----------
  16. Declare the statistic structs you need::
  17. struct mystruct {
  18. struct gnet_stats_basic bstats;
  19. struct gnet_stats_queue qstats;
  20. ...
  21. };
  22. Update statistics, in dequeue() methods only, (while owning qdisc->running)::
  23. mystruct->tstats.packet++;
  24. mystruct->qstats.backlog += skb->pkt_len;
  25. Export to userspace (Dump):
  26. ---------------------------
  27. ::
  28. my_dumping_routine(struct sk_buff *skb, ...)
  29. {
  30. struct gnet_dump dump;
  31. if (gnet_stats_start_copy(skb, TCA_STATS2, &mystruct->lock, &dump,
  32. TCA_PAD) < 0)
  33. goto rtattr_failure;
  34. if (gnet_stats_copy_basic(&dump, &mystruct->bstats) < 0 ||
  35. gnet_stats_copy_queue(&dump, &mystruct->qstats) < 0 ||
  36. gnet_stats_copy_app(&dump, &xstats, sizeof(xstats)) < 0)
  37. goto rtattr_failure;
  38. if (gnet_stats_finish_copy(&dump) < 0)
  39. goto rtattr_failure;
  40. ...
  41. }
  42. TCA_STATS/TCA_XSTATS backward compatibility:
  43. --------------------------------------------
  44. Prior users of struct tc_stats and xstats can maintain backward
  45. compatibility by calling the compat wrappers to keep providing the
  46. existing TLV types::
  47. my_dumping_routine(struct sk_buff *skb, ...)
  48. {
  49. if (gnet_stats_start_copy_compat(skb, TCA_STATS2, TCA_STATS,
  50. TCA_XSTATS, &mystruct->lock, &dump,
  51. TCA_PAD) < 0)
  52. goto rtattr_failure;
  53. ...
  54. }
  55. A struct tc_stats will be filled out during gnet_stats_copy_* calls
  56. and appended to the skb. TCA_XSTATS is provided if gnet_stats_copy_app
  57. was called.
  58. Locking:
  59. --------
  60. Locks are taken before writing and released once all statistics have
  61. been written. Locks are always released in case of an error. You
  62. are responsible for making sure that the lock is initialized.
  63. Rate Estimator:
  64. ---------------
  65. 0) Prepare an estimator attribute. Most likely this would be in user
  66. space. The value of this TLV should contain a tc_estimator structure.
  67. As usual, such a TLV needs to be 32 bit aligned and therefore the
  68. length needs to be appropriately set, etc. The estimator interval
  69. and ewma log need to be converted to the appropriate values.
  70. tc_estimator.c::tc_setup_estimator() is advisable to be used as the
  71. conversion routine. It does a few clever things. It takes a time
  72. interval in microsecs, a time constant also in microsecs and a struct
  73. tc_estimator to be populated. The returned tc_estimator can be
  74. transported to the kernel. Transfer such a structure in a TLV of type
  75. TCA_RATE to your code in the kernel.
  76. In the kernel when setting up:
  77. 1) make sure you have basic stats and rate stats setup first.
  78. 2) make sure you have initialized stats lock that is used to setup such
  79. stats.
  80. 3) Now initialize a new estimator::
  81. int ret = gen_new_estimator(my_basicstats,my_rate_est_stats,
  82. mystats_lock, attr_with_tcestimator_struct);
  83. if ret == 0
  84. success
  85. else
  86. failed
  87. From now on, every time you dump my_rate_est_stats it will contain
  88. up-to-date info.
  89. Once you are done, call gen_kill_estimator(my_basicstats,
  90. my_rate_est_stats) Make sure that my_basicstats and my_rate_est_stats
  91. are still valid (i.e still exist) at the time of making this call.
  92. Authors:
  93. --------
  94. - Thomas Graf <tgraf@suug.ch>
  95. - Jamal Hadi Salim <hadi@cyberus.ca>