[spp] [PATCH 03/10] docs: add design for spp_mirror

[x-fn-spp@sl.ntt-tx.co.jp]

From: Hideyuki Yamashita <yamashita.hideyuki@po.ntt-tx.co.jp>

Design section is for describing components and its mechanizm of
`spp_vf` and `spp_mirror`.

Signed-off-by: Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp>
Signed-off-by: Hideyuki Yamashita <yamashita.hideyuki@po.ntt-tx.co.jp>
---
 docs/guides/images/spp_vf/spp_mirror_design.svg | 564 ++++++++++++++++++++++++
 docs/guides/spp_vf/design.rst                   |  75 +++-
 2 files changed, 623 insertions(+), 16 deletions(-)
 create mode 100644 docs/guides/images/spp_vf/spp_mirror_design.svg

diff --git a/docs/guides/images/spp_vf/spp_mirror_design.svg b/docs/guides/images/spp_vf/spp_mirror_design.svg
new file mode 100644
index 0000000..bd1da65
--- /dev/null
+++ b/docs/guides/images/spp_vf/spp_mirror_design.svg
@@ -0,0 +1,564 @@
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diff --git a/docs/guides/spp_vf/design.rst b/docs/guides/spp_vf/design.rst
index fc9b014..8b9e7f3 100644
--- a/docs/guides/spp_vf/design.rst
+++ b/docs/guides/spp_vf/design.rst
@@ -6,8 +6,22 @@
 Design
 ======
 
-Components
-----------
+.. _spp_vf_design_port:
+
+Ports
+-----
+
+Both of ``spp_vf`` and ``spp_mirror`` support three types of port,
+``phy``, ``ring`` and ``vhost``.
+``phy`` port is used to retrieve packets from specific physical NIC or sent to.
+``ring`` is basically used to connect a process or a thread to make a network
+path between them.
+``vhost`` is used to forward packets from a VM or sent to.
+
+.. _spp_vf_design_spp_vf:
+
+spp_vf
+------
 
 ``spp_vf`` is a kind of secondary process and consists of several
 threads called component.
@@ -15,23 +29,23 @@ There are three types of components, ``forwarder``,
 ``merger`` and ``classifier``.
 
 .. figure:: ../images/spp_vf/spp_vf_overview.*
-    :width: 70%
+    :width: 75%
 
     SPP VF components
 
 Forwarder
-~~~~~~~~~
+^^^^^^^^^
 
 Simply forwards packets from rx to tx port.
 
 Merger
-~~~~~~
+^^^^^^
 
 Receives packets from multiple rx ports to aggregate
 packets and sends to a desctination port.
 
 Classifier
-~~~~~~~~~~
+^^^^^^^^^^
 
 Sends packets to multiple tx ports based on entries of
 MAC address and destination port in a classifier table.
@@ -43,15 +57,44 @@ which of table is referred
 if TPID (Tag Protocol Indetifier) is included in a packet and
 equals to 0x8100 as defined in IEEE 802.1Q standard.
 
+.. _spp_vf_design_spp_mirror:
 
-Ports
------
+spp_mirror
+----------
+
+``spp_mirror`` is another kind of secondary process. The keyword ``mirror``
+means that it duplicates incoming packets and forwards to additional
+destination.
+It supports only one type of component called ``mirror`` for duplicating.
+In :numref:`figure_spp_mirror_design`, incoming packets are duplicated with
+``mirror`` component and sent to original and additional destinations.
+
+.. _figure_spp_mirror_design:
+
+.. figure:: ../images/spp_vf/spp_mirror_design.*
+    :width: 45%
+
+    Spp_mirror component
+
+Mirror
+^^^^^^
+
+``mirror`` component has one ``rx`` port and two ``tx`` ports. Incoming packets
+from ``rx`` port are duplicated and sent to each of ``tx`` ports.
+
+In general, copying packet is time-consuming because it requires to make a new
+region on memory space. Considering to minimize impact for performance,
+``spp_mirror`` provides a choice of copying methods, ``shallowocopy`` or
+``deepcopy``.
+The difference between those methods is ``shallowocopy`` does not copy whole of
+packet data but share without header actually.
+``shallowcopy`` is to share mbuf between packets to get better performance
+than ``deepcopy``, but it should be used for read only for the packet.
+
+.. note::
+
+    ``shallowcopy`` calls ``rte_pktmbuf_clone()`` internally and
+    ``deepcopy`` create a new mbuf region.
 
-``spp_vf`` supports three types of PMDs, ``phy`` (Physical NIC),
-``ring`` (Ring PMD) and ``vhost`` (vhsot PMD).
-Using ``phy`` port, component can get incoming packets from outside host
-and transfer the packet to specific physical NIC.
-Using ``ring`` port, variety of combination of components can be
-configured.
-And through ``vhost`` port component can transfer packets from/to VMs.
-``port`` can also control vlan tagging and untagging.
+You should choose ``deepcopy`` if you use VLAN feature to make no change for
+original packet while copied packet is modified.
-- 
2.7.4