[RFC 0/6] Stage-Ordered API and other extensions for ring library

[Konstantin Ananyev <konstantin.v.ananyev@yandex.ru>]

From: Konstantin Ananyev <konstantin.ananyev@huawei.com>

Konstantin Ananyev (6):
  ring: common functions for 'move head' ops
  ring: make copying functions generic
  ring/soring: introduce Staged Ordered Ring
  app/test: add unit tests for soring API
  examples/l3fwd: make ACL work in pipeline and eventdev modes
  ring: minimize reads of the counterpart cache-line

The main aim of these series is to extend ring library with
new API that allows user to create/use Staged-Ordered-Ring (SORING)
abstraction. In addition to that there are few other patches that serve
different purposes:
- first two patches are just code reordering to de-duplicate
  and generalize existing rte_ring code.
- next two patches introduce SORING API into the ring library and
  provide UT for it.
- patch #5 extends l3fwd sample app to work in pipeline (worker-pool) mode. 
  Right now it is done for demonstration and performance comparison pruposes:
  it makes possible to run l3fwd in different modes:
  run-to-completion, eventdev, pipeline
  and perform sort-of 'apple-to-apple' performance comparisons.
  I am aware that in general community consensus on l3fwd is to keep its
  functionality simple and limited. From other side we already do have
  eventdev  mode for it, so why pipeline should be prohibited?
  Though if l3fwd is not an option, then we need to select some other
  existing sample app to integrate with. Probably ipsec-secgw would be the
  second best choice from my perspective, though it would require much more
  effort.
  Have to say that current l3fwd patch is way too big and unfinished,
  so if we'll decide to go forward with it, it has to be split and reworked.   
- patch #6 - attempt to optimize (by caching counter-part tail value)
  enqueue/dequeue operations for vanilla rte_ring. Logically tt is not linked
  with patches 3-5 and probably should be in a separate series.
  I put it here for now just to minimize 'Depends-on' hassle, so everyone
  can build/try everything in one go.

Seeking community help/feedback (apart from usual patch review activity):
=========================================================================
- While we tested these changes quite extensively, our platform coverage
  is limited to x86 right now.
  So would appreciate the feedback how it behaves on other architectures
  DPDK supports (ARM, PPC, etc.).
  Specially for patch #6: so far we didn't observe noticeable performance
  improvement with it on x86_64,
  So if there would be no real gain on other platforms (or scenarios) - 
  I am ok to drop that patch.
- Adding new (pipeline) mode for l3fwd sample app.
  Is it worth it? If not, what other sample app should be used to
  demonstrate new functionality we worked on? ipsec-secgw? Something else?  

SORING overview
===============
Staged-Ordered-Ring (SORING) provides a SW abstraction for 'ordered' queues
with multiple processing 'stages'. It is based on conventional DPDK rte_ring,
re-uses many of its concepts, and even substantial part of its code.
It can be viewed as an 'extension' of rte_ring functionality.
In particular, main SORING properties:
- circular ring buffer with fixed size objects
- producer, consumer plus multiple processing stages in between.
- allows to split objects processing into multiple stages.
- objects remain in the same ring while moving from one stage to the other,
  initial order is preserved, no extra copying needed.
- preserves the ingress order of objects within the queue across multiple
  stages
- each stage (and producer/consumer) can be served by single and/or
  multiple threads.
- number of stages, size and number of objects in the ring are
 configurable at ring initialization time.

Data-path API provides four main operations:
- enqueue/dequeue works in the same manner as for conventional rte_ring,
  all rte_ring synchronization types are supported.
- acquire/release - for each stage there is an acquire (start) and
  release (finish) operation. After some objects are 'acquired' - given thread
  can safely assume that it has exclusive ownership of these objects till
  it will invoke 'release' for them.
  After 'release', objects can be 'acquired' by next stage and/or dequeued
  by the consumer (in case of last stage).

Expected use-case: applications that uses pipeline model
(probably with multiple stages) for packet processing, when preserving
incoming packet order is important.

The concept of ‘ring with stages’ is similar to DPDK OPDL eventdev PMD [1],
but the internals are different.  
In particular, SORING maintains internal array of 'states' for each element
in the ring that is  shared by all threads/processes that access the ring.
That allows 'release' to avoid excessive waits on the tail value and helps
to improve performancei and scalability.     
In terms of performance, with our measurements rte_soring and
conventional rte_ring provide nearly identical numbers.
As an example, on our SUT: Intel ICX CPU @ 2.00GHz, 
l3fwd (--lookup=acl) in pipeline mode (see patch #5 for details) both
rte_ring and rte_soring reach ~20Mpps for single I/O lcore and same
number of worker lcores.

[1] https://www.dpdk.org/wp-content/uploads/sites/35/2018/06/DPDK-China2017-Ma-OPDL.pdf

 app/test/meson.build               |   3 +
 app/test/test_soring.c             | 452 ++++++++++++++++
 app/test/test_soring_mt_stress.c   |  45 ++
 app/test/test_soring_stress.c      |  48 ++
 app/test/test_soring_stress.h      |  35 ++
 app/test/test_soring_stress_impl.h | 832 +++++++++++++++++++++++++++++
 drivers/net/mlx5/mlx5_hws_cnt.h    |   5 +-
 drivers/net/ring/rte_eth_ring.c    |   2 +-
 examples/l3fwd/l3fwd.h             |  55 ++
 examples/l3fwd/l3fwd_acl.c         | 125 ++++-
 examples/l3fwd/l3fwd_acl_event.h   | 258 +++++++++
 examples/l3fwd/l3fwd_event.c       |  14 +
 examples/l3fwd/l3fwd_event.h       |   1 +
 examples/l3fwd/l3fwd_sse.h         |  49 +-
 examples/l3fwd/l3fwd_wqp.c         | 274 ++++++++++
 examples/l3fwd/l3fwd_wqp.h         | 132 +++++
 examples/l3fwd/main.c              |  75 ++-
 examples/l3fwd/meson.build         |   1 +
 lib/ring/meson.build               |   4 +-
 lib/ring/rte_ring.c                |   6 +-
 lib/ring/rte_ring_c11_pvt.h        | 134 +----
 lib/ring/rte_ring_core.h           |  12 +-
 lib/ring/rte_ring_elem_pvt.h       | 183 +++++--
 lib/ring/rte_ring_generic_pvt.h    | 153 ++----
 lib/ring/rte_ring_hts_elem_pvt.h   |  85 +--
 lib/ring/rte_ring_peek_elem_pvt.h  |   4 +-
 lib/ring/rte_ring_rts_elem_pvt.h   |  85 +--
 lib/ring/rte_soring.c              | 144 +++++
 lib/ring/rte_soring.h              | 270 ++++++++++
 lib/ring/soring.c                  | 446 ++++++++++++++++
 lib/ring/soring.h                  | 124 +++++
 lib/ring/version.map               |  13 +
 32 files changed, 3632 insertions(+), 437 deletions(-)
 create mode 100644 app/test/test_soring.c
 create mode 100644 app/test/test_soring_mt_stress.c
 create mode 100644 app/test/test_soring_stress.c
 create mode 100644 app/test/test_soring_stress.h
 create mode 100644 app/test/test_soring_stress_impl.h
 create mode 100644 examples/l3fwd/l3fwd_acl_event.h
 create mode 100644 examples/l3fwd/l3fwd_wqp.c
 create mode 100644 examples/l3fwd/l3fwd_wqp.h
 create mode 100644 lib/ring/rte_soring.c
 create mode 100644 lib/ring/rte_soring.h
 create mode 100644 lib/ring/soring.c
 create mode 100644 lib/ring/soring.h

-- 
2.35.3