|author||Jasvinder Singh <email@example.com>||2017-07-25 18:40:51 +0100|
|committer||Thomas Monjalon <firstname.lastname@example.org>||2017-08-04 01:07:08 +0200|
doc: describe traffic management API
This patch adds description of the traffic management api to dpdk programmers guide. Signed-off-by: Jasvinder Singh <email@example.com> Signed-off-by: Cristian Dumitrescu <firstname.lastname@example.org> Acked-by: John McNamara <email@example.com>
2 files changed, 252 insertions, 0 deletions
diff --git a/doc/guides/prog_guide/index.rst b/doc/guides/prog_guide/index.rst
index 5548aba..13e03db 100644
@@ -44,6 +44,7 @@ Programmer's Guide
diff --git a/doc/guides/prog_guide/traffic_management.rst b/doc/guides/prog_guide/traffic_management.rst
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+.. BSD LICENSE
+ Copyright(c) 2017 Intel Corporation. All rights reserved.
+ All rights reserved.
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions
+ are met:
+ * Redistributions of source code must retain the above copyright
+ notice, this list of conditions and the following disclaimer.
+ * Redistributions in binary form must reproduce the above copyright
+ notice, this list of conditions and the following disclaimer in
+ the documentation and/or other materials provided with the
+ * Neither the name of Intel Corporation nor the names of its
+ contributors may be used to endorse or promote products derived
+ from this software without specific prior written permission.
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+Traffic Management API
+This is the generic API for the Quality of Service (QoS) Traffic Management of
+Ethernet devices, which includes the following main features: hierarchical
+scheduling, traffic shaping, congestion management, packet marking. This API
+is agnostic of the underlying HW, SW or mixed HW-SW implementation.
+* Part of DPDK rte_ethdev API
+* Capability query API per port, per hierarchy level and per hierarchy node
+* Scheduling algorithms: Strict Priority (SP), Weighed Fair Queuing (WFQ)
+* Traffic shaping: single/dual rate, private (per node) and
+ shared (by multiple nodes) shapers
+* Congestion management for hierarchy leaf nodes: algorithms of tail drop, head
+ drop, WRED, private (per node) and shared (by multiple nodes) WRED contexts
+* Packet marking: IEEE 802.1q (VLAN DEI), IETF RFC 3168 (IPv4/IPv6 ECN for TCP
+ and SCTP), IETF RFC 2597 (IPv4 / IPv6 DSCP)
+The aim of these APIs is to advertise the capability information (i.e critical
+parameter values) that the TM implementation (HW/SW) is able to support for the
+application. The APIs supports the information disclosure at the TM level, at
+any hierarchical level of the TM and at any node level of the specific
+hierarchical level. Such information helps towards rapid understanding of
+whether a specific implementation does meet the needs to the user application.
+At the TM level, users can get high level idea with the help of various
+parameters such as maximum number of nodes, maximum number of hierarchical
+levels, maximum number of shapers, maximum number of private shapers, type of
+scheduling algorithm (Strict Priority, Weighted Fair Queueing , etc.), etc.,
+supported by the implementation.
+Likewise, users can query the capability of the TM at the hierarchical level to
+have more granular knowledge about the specific level. The various parameters
+such as maximum number of nodes at the level, maximum number of leaf/non-leaf
+nodes at the level, type of the shaper(dual rate, single rate) supported at
+the level if node is non-leaf type etc., are exposed as a result of
+hierarchical level capability query.
+Finally, the node level capability API offers knowledge about the capability
+supported by the node at any specific level. The information whether the
+support is available for private shaper, dual rate shaper, maximum and minimum
+shaper rate, etc. is exposed by node level capability API.
+The fundamental scheduling algorithms that are supported are Strict Priority
+(SP) and Weighted Fair Queuing (WFQ). The SP and WFQ algorithms are supported
+at the level of each node of the scheduling hierarchy, regardless of the node
+level/position in the tree. The SP algorithm is used to schedule between
+sibling nodes with different priority, while WFQ is used to schedule between
+groups of siblings that have the same priority.
+Algorithms such as Weighed Round Robin (WRR), byte-level WRR, Deficit WRR
+(DWRR), etc are considered approximations of the ideal WFQ and are therefore
+assimilated to WFQ, although an associated implementation-dependent accuracy,
+performance and resource usage trade-off might exist.
+The TM API provides support for single rate and dual rate shapers (rate
+limiters) for the hierarchy nodes, subject to the specific implementation
+support being available.
+Each hierarchy node has zero or one private shaper (only one node using it)
+and/or zero, one or several shared shapers (multiple nodes use the same shaper
+instance). A private shaper is used to perform traffic shaping for a single
+node, while a shared shaper is used to perform traffic shaping for a group of
+The configuration of private and shared shapers is done through the definition
+of shaper profiles. Any shaper profile (single rate or dual rate shaper) can be
+used by one or several shaper instances (either private or shared).
+Single rate shapers use a single token bucket. Therefore, single rate shaper is
+configured by setting the rate of the committed bucket to zero, which
+effectively disables this bucket. The peak bucket is used to limit the rate
+and the burst size for the single rate shaper. Dual rate shapers use both the
+committed and the peak token buckets. The rate of the peak bucket has to be
+bigger than zero, as well as greater than or equal to the rate of the committed
+Congestion management is used to control the admission of packets into a packet
+queue or group of packet queues on congestion. The congestion management
+algorithms that are supported are: Tail Drop, Head Drop and Weighted Random
+Early Detection (WRED). They are made available for every leaf node in the
+hierarchy, subject to the specific implementation supporting them.
+On request of writing a new packet into the current queue while the queue is
+full, the Tail Drop algorithm drops the new packet while leaving the queue
+unmodified, as opposed to the Head Drop* algorithm, which drops the packet
+at the head of the queue (the oldest packet waiting in the queue) and admits
+the new packet at the tail of the queue.
+The Random Early Detection (RED) algorithm works by proactively dropping more
+and more input packets as the queue occupancy builds up. When the queue is full
+or almost full, RED effectively works as Tail Drop. The Weighted RED (WRED)
+algorithm uses a separate set of RED thresholds for each packet color and uses
+separate set of RED thresholds for each packet color.
+Each hierarchy leaf node with WRED enabled as its congestion management mode
+has zero or one private WRED context (only one leaf node using it) and/or zero,
+one or several shared WRED contexts (multiple leaf nodes use the same WRED
+context). A private WRED context is used to perform congestion management for
+a single leaf node, while a shared WRED context is used to perform congestion
+management for a group of leaf nodes.
+The configuration of WRED private and shared contexts is done through the
+definition of WRED profiles. Any WRED profile can be used by one or several
+WRED contexts (either private or shared).
+The TM APIs have been provided to support various types of packet marking such
+as VLAN DEI packet marking (IEEE 802.1Q), IPv4/IPv6 ECN marking of TCP and SCTP
+packets (IETF RFC 3168) and IPv4/IPv6 DSCP packet marking (IETF RFC 2597).
+All VLAN frames of a given color get their DEI bit set if marking is enabled
+for this color. In case, when marking for a given color is not enabled, the
+DEI bit is left as is (either set or not).
+All IPv4/IPv6 packets of a given color with ECN set to 2’b01 or 2’b10 carrying
+TCP or SCTP have their ECN set to 2’b11 if the marking feature is enabled for
+the current color, otherwise the ECN field is left as is.
+All IPv4/IPv6 packets have their color marked into DSCP bits 3 and 4 as
+follows: green mapped to Low Drop Precedence (2’b01), yellow to Medium (2’b10)
+and red to High (2’b11). Marking needs to be explicitly enabled for each color;
+when not enabled for a given color, the DSCP field of all packets with that
+color is left as is.
+Steps to Setup the Hierarchy
+The TM hierarchical tree consists of leaf nodes and non-leaf nodes. Each leaf
+node sits on top of a scheduling queue of the current Ethernet port. Therefore,
+the leaf nodes have predefined IDs in the range of 0... (N-1), where N is the
+number of scheduling queues of the current Ethernet port. The non-leaf nodes
+have their IDs generated by the application outside of the above range, which
+is reserved for leaf nodes.
+Each non-leaf node has multiple inputs (its children nodes) and single output
+(which is input to its parent node). It arbitrates its inputs using Strict
+Priority (SP) and Weighted Fair Queuing (WFQ) algorithms to schedule input
+packets to its output while observing its shaping (rate limiting) constraints.
+The children nodes with different priorities are scheduled using the SP
+algorithm based on their priority, with 0 as the highest priority. Children
+with the same priority are scheduled using the WFQ algorithm according to their
+weights. The WFQ weight of a given child node is relative to the sum of the
+weights of all its sibling nodes that have the same priority, with 1 as the
+lowest weight. For each SP priority, the WFQ weight mode can be set as either
+byte-based or packet-based.
+Initial Hierarchy Specification
+The hierarchy is specified by incrementally adding nodes to build up the
+scheduling tree. The first node that is added to the hierarchy becomes the root
+node and all the nodes that are subsequently added have to be added as
+descendants of the root node. The parent of the root node has to be specified
+as RTE_TM_NODE_ID_NULL and there can only be one node with this parent ID
+(i.e. the root node). The unique ID that is assigned to each node when the node
+is created is further used to update the node configuration or to connect
+children nodes to it.
+During this phase, some limited checks on the hierarchy specification can be
+conducted, usually limited in scope to the current node, its parent node and
+its sibling nodes. At this time, since the hierarchy is not fully defined,
+there is typically no real action performed by the underlying implementation.
+The hierarchy commit API is called during the port initialization phase (before
+the Ethernet port is started) to freeze the start-up hierarchy. This function
+typically performs the following steps:
+* It validates the start-up hierarchy that was previously defined for the
+ current port through successive node add API invocations.
+* Assuming successful validation, it performs all the necessary implementation
+ specific operations to install the specified hierarchy on the current port,
+ with immediate effect once the port is started.
+This function fails when the currently configured hierarchy is not supported by
+the Ethernet port, in which case the user can abort or try out another
+hierarchy configuration (e.g. a hierarchy with less leaf nodes), which can be
+built from scratch or by modifying the existing hierarchy configuration. Note
+that this function can still fail due to other causes (e.g. not enough memory
+available in the system, etc.), even though the specified hierarchy is
+supported in principle by the current port.
+Run-Time Hierarchy Updates
+The TM API provides support for on-the-fly changes to the scheduling hierarchy,
+thus operations such as node add/delete, node suspend/resume, parent node
+update, etc., can be invoked after the Ethernet port has been started, subject
+to the specific implementation supporting them. The set of dynamic updates
+supported by the implementation is advertised through the port capability set.