[dpdk-dev] [RFC PATCH 0/7] RFC:EventDev OPDL PMD

[liang.j.ma@intel.com]

From: Liang Ma <liang.j.ma@intel.com>

The OPDL (Ordered Packet Distribution Library) eventdev is a specific
implementation of the eventdev API. It is particularly suited to packet
processing workloads that have high throughput and low latency 
requirements. All packets follow the same path through the device.
The order which packets  follow is determinted by the order in which
queues are set up. Packets are left on the ring until they are transmitted.
As a result packets do not go out of order.

Features:

The OPDL eventdev implements a subset of features of the eventdev API;

Queues
 * Atomic
 * Ordered (Parallel is supported as parallel is a subset of Ordered)
 * Single-Link

Ports
 * Load balanced (for Atomic, Ordered, Parallel queues)
 * Single Link (for single-link queues)

Single Port Queue

It is possible to create a Single Port Queue 
RTE_EVENT_QUEUE_CFG_SINGLE_LINK. Packets dequeued from this queue do
not need to be re-enqueued (as is the case with an ordered queue). The 
purpose of this queue is to allow for asynchronous handling of packets in 
the middle of a pipeline. Ordered queues in the middle of a pipeline 
cannot delete packets.


Queue Dependencies

As stated the order in which packets travel through queues is static in
nature. They go through the queues in the order the queues are setup at
initialisation rte_event_queue_setup(). For example if an application
sets up 3 queues, Q0, Q1, Q2 and has 3 assoicated ports P0, P1, P2 and 
P3 then packets must be

 * Enqueued onto Q0 (typically through P0), then

 * Dequeued from Q0 (typically through P1), then

 * Enqueued onto Q1 (also through P1), then

 * Dequeued from Q2 (typically through P2),  then

 * Enqueued onto Q3 (also through P2), then

 * Dequeued from Q3 (typically through P3) and then transmitted on the 
   relevant eth port


Limitations

The opdl implementation has a number of limitations. These limitations are
due to the static nature of the underlying queues. It is because of this
that the implementation can achieve such high throughput and low latency

The following list is a comprehensive outline of the what is supported and
the limitations / restrictions imposed by the opdl pmd

 - The order in which packets moved between queues is static and fixed 
   (dynamic scheduling is not supported).

 - NEW, RELEASE op type are not explicitly supported. RX (first enqueue) 
   implicitly adds NEW event types, and TX (last dequeue) implicitly does
   RELEASE event types.

 - All packets follow the same path through device queues.

 - Flows within queues are NOT supported.

 - Event priority is NOT supported.

 - Once the device is stopped all inflight events are lost. Applications should 
   clear all inflight events before stopping it.

 - Each port can only be associated with one queue.

 - Each queue can have multiple ports associated with it.

 - Each worker core has to dequeue the maximum burst size for that port.

 - For performance, the rte_event flow_id should not be updated once 
    packet is enqueued on RX.

Reference
General concept of event driven programming model
[http://dpdk.org/doc/guides/eventdevs/index.html]

Original Ordered Pipeline Design slides 
[https://dpdksummit.com/Archive/pdf/2017Asia/DPDK-China2017-Ma-OPDL.pdf]


Liang Ma (7):
  event/opdl:  add the opdl ring infrastructure library
  event/opdl: add the opdl pmd header and init helper function
  event/opdl: add the opdl pmd main body and xstats helper function
  event/opdl: update the build system to enable compilation of pmd
  test/eventdev: opdl eventdev pmd unit test func and makefiles
  examples/eventdev_pipeline_opdl: adding example
  doc: add eventdev opdl pmd docuement and example usage document

 config/common_base                                 |    6 +
 doc/guides/eventdevs/index.rst                     |    1 +
 doc/guides/eventdevs/opdl.rst                      |  162 +++
 .../sample_app_ug/eventdev_pipeline_opdl_pmd.rst   |  128 +++
 doc/guides/sample_app_ug/index.rst                 |    1 +
 drivers/event/Makefile                             |    1 +
 drivers/event/opdl/Makefile                        |   65 ++
 drivers/event/opdl/opdl_evdev.c                    |  714 ++++++++++++
 drivers/event/opdl/opdl_evdev.h                    |  353 ++++++
 drivers/event/opdl/opdl_evdev_init.c               |  945 ++++++++++++++++
 drivers/event/opdl/opdl_evdev_xstats.c             |  205 ++++
 drivers/event/opdl/opdl_ring.c                     | 1170 ++++++++++++++++++++
 drivers/event/opdl/opdl_ring.h                     |  578 ++++++++++
 drivers/event/opdl/rte_pmd_evdev_opdl_version.map  |    3 +
 examples/eventdev_pipeline_opdl_pmd/Makefile       |   49 +
 examples/eventdev_pipeline_opdl_pmd/main.c         |  766 +++++++++++++
 mk/rte.app.mk                                      |    1 +
 test/test/Makefile                                 |    1 +
 test/test/test_eventdev_opdl.c                     | 1089 ++++++++++++++++++
 19 files changed, 6238 insertions(+)
 create mode 100644 doc/guides/eventdevs/opdl.rst
 create mode 100644 doc/guides/sample_app_ug/eventdev_pipeline_opdl_pmd.rst
 create mode 100644 drivers/event/opdl/Makefile
 create mode 100644 drivers/event/opdl/opdl_evdev.c
 create mode 100644 drivers/event/opdl/opdl_evdev.h
 create mode 100644 drivers/event/opdl/opdl_evdev_init.c
 create mode 100644 drivers/event/opdl/opdl_evdev_xstats.c
 create mode 100644 drivers/event/opdl/opdl_ring.c
 create mode 100644 drivers/event/opdl/opdl_ring.h
 create mode 100644 drivers/event/opdl/rte_pmd_evdev_opdl_version.map
 create mode 100644 examples/eventdev_pipeline_opdl_pmd/Makefile
 create mode 100644 examples/eventdev_pipeline_opdl_pmd/main.c
 create mode 100644 test/test/test_eventdev_opdl.c

-- 
2.7.5

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