diff options
Diffstat (limited to 'docs/development/requirements/03-dpdk.rst')
| -rw-r--r-- | docs/development/requirements/03-dpdk.rst | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/docs/development/requirements/03-dpdk.rst b/docs/development/requirements/03-dpdk.rst new file mode 100644 index 00000000..ad7c8c78 --- /dev/null +++ b/docs/development/requirements/03-dpdk.rst @@ -0,0 +1,170 @@ +.. This work is licensed under a Creative Commons Attribution 4.0 International License. +.. http://creativecommons.org/licenses/by/4.0 +.. (c) OPNFV, Intel Corporation and others. + +DPDK Enhancements +================== +This section will discuss the Barometer features that were integrated with DPDK. + +Measuring Telco Traffic and Performance KPIs +-------------------------------------------- +This section will discuss the Barometer features that enable Measuring Telco Traffic +and Performance KPIs. + +.. Figure:: stats_and_timestamps.png + + Measuring Telco Traffic and Performance KPIs + +* The very first thing Barometer enabled was a call-back API in DPDK and an + associated application that used the API to demonstrate how to timestamp + packets and measure packet latency in DPDK (the sample app is called + rxtx_callbacks). This was upstreamed to DPDK 2.0 and is represented by + the interfaces 1 and 2 in Figure 1.2. + +* The second thing Barometer implemented in DPDK is the extended NIC statistics API, + which exposes NIC stats including error stats to the DPDK user by reading the + registers on the NIC. This is represented by interface 3 in Figure 1.2. + + * For DPDK 2.1 this API was only implemented for the ixgbe (10Gb) NIC driver, + in association with a sample application that runs as a DPDK secondary + process and retrieves the extended NIC stats. + + * For DPDK 2.2 the API was implemented for igb, i40e and all the Virtual + Functions (VFs) for all drivers. + + * For DPDK 16.07 the API migrated from using string value pairs to using id + value pairs, improving the overall performance of the API. + +Monitoring DPDK interfaces +-------------------------- +With the features Barometer enabled in DPDK to enable measuring Telco traffic and +performance KPIs, we can now retrieve NIC statistics including error stats and +relay them to a DPDK user. The next step is to enable monitoring of the DPDK +interfaces based on the stats that we are retrieving from the NICs, by relaying +the information to a higher level Fault Management entity. To enable this Barometer +has been enabling a number of plugins for collectd. + +DPDK Keep Alive description +--------------------------- +SFQM aims to enable fault detection within DPDK, the very first feature to +meet this goal is the DPDK Keep Alive Sample app that is part of DPDK 2.2. + +DPDK Keep Alive or KA is a sample application that acts as a heartbeat/watchdog +for DPDK packet processing cores, to detect application thread failure. The +application supports the detection of ‘failed’ DPDK cores and notification to a +HA/SA middleware. The purpose is to detect Packet Processing Core fails (e.g. +infinite loop) and ensure the failure of the core does not result in a fault +that is not detectable by a management entity. + +.. Figure:: dpdk_ka.png + + DPDK Keep Alive Sample Application + +Essentially the app demonstrates how to detect 'silent outages' on DPDK packet +processing cores. The application can be decomposed into two specific parts: +detection and notification. + +* The detection period is programmable/configurable but defaults to 5ms if no + timeout is specified. +* The Notification support is enabled by simply having a hook function that where this + can be 'call back support' for a fault management application with a compliant + heartbeat mechanism. + +DPDK Keep Alive Sample App Internals +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +This section provides some explanation of the The Keep-Alive/'Liveliness' +conceptual scheme as well as the DPDK Keep Alive App. The initialization and +run-time paths are very similar to those of the L2 forwarding application (see +`L2 Forwarding Sample Application (in Real and Virtualized Environments)`_ for more +information). + +There are two types of cores: a Keep Alive Monitor Agent Core (master DPDK core) +and Worker cores (Tx/Rx/Forwarding cores). The Keep Alive Monitor Agent Core +will supervise worker cores and report any failure (2 successive missed pings). +The Keep-Alive/'Liveliness' conceptual scheme is: + +* DPDK worker cores mark their liveliness as they forward traffic. +* A Keep Alive Monitor Agent Core runs a function every N Milliseconds to + inspect worker core liveliness. +* If keep-alive agent detects time-outs, it notifies the fault management + entity through a call-back function. + +**Note:** Only the worker cores state is monitored. There is no mechanism or agent +to monitor the Keep Alive Monitor Agent Core. + +DPDK Keep Alive Sample App Code Internals +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The following section provides some explanation of the code aspects that are +specific to the Keep Alive sample application. + +The heartbeat functionality is initialized with a struct rte_heartbeat and the +callback function to invoke in the case of a timeout. + +.. code:: c + + rte_global_keepalive_info = rte_keepalive_create(&dead_core, NULL); + if (rte_global_hbeat_info == NULL) + rte_exit(EXIT_FAILURE, "keepalive_create() failed"); + +The function that issues the pings hbeat_dispatch_pings() is configured to run +every check_period milliseconds. + +.. code:: c + + if (rte_timer_reset(&hb_timer, + (check_period * rte_get_timer_hz()) / 1000, + PERIODICAL, + rte_lcore_id(), + &hbeat_dispatch_pings, rte_global_keepalive_info + ) != 0 ) + rte_exit(EXIT_FAILURE, "Keepalive setup failure.\n"); + +The rest of the initialization and run-time path follows the same paths as the +the L2 forwarding application. The only addition to the main processing loop is +the mark alive functionality and the example random failures. + +.. code:: c + + rte_keepalive_mark_alive(&rte_global_hbeat_info); + cur_tsc = rte_rdtsc(); + + /* Die randomly within 7 secs for demo purposes.. */ + if (cur_tsc - tsc_initial > tsc_lifetime) + break; + +The rte_keepalive_mark_alive() function simply sets the core state to alive. + +.. code:: c + + static inline void + rte_keepalive_mark_alive(struct rte_heartbeat *keepcfg) + { + keepcfg->state_flags[rte_lcore_id()] = 1; + } + +Keep Alive Monitor Agent Core Monitoring Options +The application can run on either a host or a guest. As such there are a number +of options for monitoring the Keep Alive Monitor Agent Core through a Local +Agent on the compute node: + + ====================== ========== ============= + Application Location DPDK KA LOCAL AGENT + ====================== ========== ============= + HOST X HOST/GUEST + GUEST X HOST/GUEST + ====================== ========== ============= + + +For the first implementation of a Local Agent SFQM will enable: + + ====================== ========== ============= + Application Location DPDK KA LOCAL AGENT + ====================== ========== ============= + HOST X HOST + ====================== ========== ============= + +Through extending the dpdkstat plugin for collectd with KA functionality, and +integrating the extended plugin with Monasca for high performing, resilient, +and scalable fault detection. + +.. _L2 Forwarding Sample Application (in Real and Virtualized Environments): http://dpdk.org/doc/guides/sample_app_ug/l2_forward_real_virtual.html |