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Diffstat (limited to 'Documentation/networking/gen_stats.rst')
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diff --git a/Documentation/networking/gen_stats.rst b/Documentation/networking/gen_stats.rst new file mode 100644 index 000000000000..595a83b9a61b --- /dev/null +++ b/Documentation/networking/gen_stats.rst @@ -0,0 +1,129 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============================================== +Generic networking statistics for netlink users +=============================================== + +Statistic counters are grouped into structs: + +==================== ===================== ===================== +Struct TLV type Description +==================== ===================== ===================== +gnet_stats_basic TCA_STATS_BASIC Basic statistics +gnet_stats_rate_est TCA_STATS_RATE_EST Rate estimator +gnet_stats_queue TCA_STATS_QUEUE Queue statistics +none TCA_STATS_APP Application specific +==================== ===================== ===================== + + +Collecting: +----------- + +Declare the statistic structs you need:: + + struct mystruct { + struct gnet_stats_basic bstats; + struct gnet_stats_queue qstats; + ... + }; + +Update statistics, in dequeue() methods only, (while owning qdisc->running):: + + mystruct->tstats.packet++; + mystruct->qstats.backlog += skb->pkt_len; + + +Export to userspace (Dump): +--------------------------- + +:: + + my_dumping_routine(struct sk_buff *skb, ...) + { + struct gnet_dump dump; + + if (gnet_stats_start_copy(skb, TCA_STATS2, &mystruct->lock, &dump, + TCA_PAD) < 0) + goto rtattr_failure; + + if (gnet_stats_copy_basic(&dump, &mystruct->bstats) < 0 || + gnet_stats_copy_queue(&dump, &mystruct->qstats) < 0 || + gnet_stats_copy_app(&dump, &xstats, sizeof(xstats)) < 0) + goto rtattr_failure; + + if (gnet_stats_finish_copy(&dump) < 0) + goto rtattr_failure; + ... + } + +TCA_STATS/TCA_XSTATS backward compatibility: +-------------------------------------------- + +Prior users of struct tc_stats and xstats can maintain backward +compatibility by calling the compat wrappers to keep providing the +existing TLV types:: + + my_dumping_routine(struct sk_buff *skb, ...) + { + if (gnet_stats_start_copy_compat(skb, TCA_STATS2, TCA_STATS, + TCA_XSTATS, &mystruct->lock, &dump, + TCA_PAD) < 0) + goto rtattr_failure; + ... + } + +A struct tc_stats will be filled out during gnet_stats_copy_* calls +and appended to the skb. TCA_XSTATS is provided if gnet_stats_copy_app +was called. + + +Locking: +-------- + +Locks are taken before writing and released once all statistics have +been written. Locks are always released in case of an error. You +are responsible for making sure that the lock is initialized. + + +Rate Estimator: +--------------- + +0) Prepare an estimator attribute. Most likely this would be in user + space. The value of this TLV should contain a tc_estimator structure. + As usual, such a TLV needs to be 32 bit aligned and therefore the + length needs to be appropriately set, etc. The estimator interval + and ewma log need to be converted to the appropriate values. + tc_estimator.c::tc_setup_estimator() is advisable to be used as the + conversion routine. It does a few clever things. It takes a time + interval in microsecs, a time constant also in microsecs and a struct + tc_estimator to be populated. The returned tc_estimator can be + transported to the kernel. Transfer such a structure in a TLV of type + TCA_RATE to your code in the kernel. + +In the kernel when setting up: + +1) make sure you have basic stats and rate stats setup first. +2) make sure you have initialized stats lock that is used to setup such + stats. +3) Now initialize a new estimator:: + + int ret = gen_new_estimator(my_basicstats,my_rate_est_stats, + mystats_lock, attr_with_tcestimator_struct); + + if ret == 0 + success + else + failed + +From now on, every time you dump my_rate_est_stats it will contain +up-to-date info. + +Once you are done, call gen_kill_estimator(my_basicstats, +my_rate_est_stats) Make sure that my_basicstats and my_rate_est_stats +are still valid (i.e still exist) at the time of making this call. + + +Authors: +-------- +- Thomas Graf <tgraf@suug.ch> +- Jamal Hadi Salim <hadi@cyberus.ca> |