[dpdk-dev] [PATCH] doc: add Vector FM10K introductions

["Chen Jing D(Mark)" <jing.d.chen@intel.com>]

From: "Chen Jing D(Mark)" <jing.d.chen@intel.com>

Add introductions on how to enable Vector FM10K Rx/Tx functions,
the preconditions and assumptions on Rx/Tx configuration parameters.
The new content also lists the limitations of vector, so app/customer
can do better to select best Rx/Tx functions.

Signed-off-by: Chen Jing D(Mark) <jing.d.chen@intel.com>
---
 doc/guides/nics/fm10k.rst |   89 +++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 89 insertions(+), 0 deletions(-)

diff --git a/doc/guides/nics/fm10k.rst b/doc/guides/nics/fm10k.rst
index 4206b7f..54b761c 100644
--- a/doc/guides/nics/fm10k.rst
+++ b/doc/guides/nics/fm10k.rst
@@ -34,6 +34,95 @@ FM10K Poll Mode Driver
 The FM10K poll mode driver library provides support for the Intel FM10000
 (FM10K) family of 40GbE/100GbE adapters.
 
+Vector PMD for FM10K
+--------------------
+Vector PMD uses Intel® SIMD instructions to optimize packet I/O.
+It improves load/store bandwidth efficiency of L1 data cache by using a wider
+SSE/AVX register 1 (1).
+The wider register gives space to hold multiple packet buffers so as to save
+instruction number when processing bulk of packets.
+
+There is no change to PMD API. The RX/TX handler are the only two entries for
+vPMD packet I/O. They are transparently registered at runtime RX/TX execution
+if all condition checks pass.
+
+1.  To date, only an SSE version of FM10K vPMD is available.
+    To ensure that vPMD is in the binary code, ensure that the option
+    CONFIG_RTE_LIBRTE_FM10K_INC_VECTOR=y is in the configure file.
+
+Some constraints apply as pre-conditions for specific optimizations on bulk
+packet transfers. The following sections explain RX and TX constraints in the
+vPMD.
+
+RX Constraints
+~~~~~~~~~~~~~~
+
+Prerequisites and Pre-conditions
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Number of descriptor ring must be power of 2. This is the assumptions for
+Vector RX. With this pre-condition, ring pointer can easily scroll back to head
+after hitting tail without conditional check. Besides that, Vector RX can use
+it to do bit mask by ``ring_size - 1``.
+
+Feature not Supported by Vector RX PMD
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Some features are not supported when trying to increase the throughput in vPMD.
+They are:
+
+*   IEEE1588
+
+*   FDIR
+
+*   Header split
+
+*   RX checksum offload
+
+Other features are supported using optional MACRO configuration. They include:
+
+*   HW VLAN strip
+
+*   L3/L4 packet type
+
+To enabled by RX_OLFLAGS (RTE_LIBRTE_FM10K_RX_OLFLAGS_ENABLE=y)
+
+To guarantee the constraint, configuration flags in dev_conf.rxmode will be
+checked:
+
+*   hw_vlan_extend
+
+*   hw_ip_checksum
+
+*   header_split
+
+*   fdir_conf->mode
+
+RX Burst Size
+^^^^^^^^^^^^^
+
+As vPMD is focused on high throughput, which processes 4 packets at a time.
+So it assumes that the RX burst should be greater than 4 per burst. It returns
+zero if using nb_pkt < 4 in the receive handler. If nb_pkt is not multiple of
+4, a floor alignment will be applied.
+
+TX Constraint
+~~~~~~~~~~~~~
+
+Feature not Supported by TX Vector PMD
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+TX vPMD only works when txq_flags is set to FM10K_SIMPLE_TX_FLAG.
+This means that it does not support TX multi-segment, VLAN offload and TX csum
+offload. The following MACROs are used for these three features:
+
+*   ETH_TXQ_FLAGS_NOMULTSEGS
+
+*   ETH_TXQ_FLAGS_NOVLANOFFL
+
+*   ETH_TXQ_FLAGS_NOXSUMSCTP
+
+*   ETH_TXQ_FLAGS_NOXSUMUDP
+
+*   ETH_TXQ_FLAGS_NOXSUMTCP
 
 Limitations
 -----------
-- 
1.7.7.6