aaee1d15cb
Move the "source_org" page to after overview, where it fits better to explain the source-code layout of DPDK, before getting into details of specific libraries such as EAL. Also removes the older titles from the 3 documents which still had them. Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
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161 lines
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.. SPDX-License-Identifier: BSD-3-Clause
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Copyright(c) 2010-2014 Intel Corporation.
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Overview
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========
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This section gives a global overview of the architecture of Data Plane Development Kit (DPDK).
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The main goal of the DPDK is to provide a simple,
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complete framework for fast packet processing in data plane applications.
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Users may use the code to understand some of the techniques employed,
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to build upon for prototyping or to add their own protocol stacks.
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Alternative ecosystem options that use the DPDK are available.
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The framework creates a set of libraries for specific environments
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through the creation of an Environment Abstraction Layer (EAL),
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which may be specific to a mode of the Intel® architecture (32-bit or 64-bit),
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Linux* user space compilers or a specific platform.
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These environments are created through the use of meson files and configuration files.
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Once the EAL library is created, the user may link with the library to create their own applications.
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Other libraries, outside of EAL, including the Hash,
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Longest Prefix Match (LPM) and rings libraries are also provided.
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Sample applications are provided to help show the user how to use various features of the DPDK.
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The DPDK implements a run to completion model for packet processing,
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where all resources must be allocated prior to calling Data Plane applications,
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running as execution units on logical processing cores.
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The model does not support a scheduler and all devices are accessed by polling.
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The primary reason for not using interrupts is the performance overhead imposed by interrupt processing.
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In addition to the run-to-completion model,
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a pipeline model may also be used by passing packets or messages between cores via the rings.
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This allows work to be performed in stages and may allow more efficient use of code on cores.
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Development Environment
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-----------------------
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The DPDK project installation requires Linux and the associated toolchain,
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such as one or more compilers, assembler, meson utility,
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editor and various libraries to create the DPDK components and libraries.
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Once these libraries are created for the specific environment and architecture,
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they may then be used to create the user's data plane application.
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When creating applications for the Linux user space, the glibc library is used.
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See the *DPDK Getting Started Guide* for information on setting up the development environment.
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Environment Abstraction Layer
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-----------------------------
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The Environment Abstraction Layer (EAL) provides a generic interface
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that hides the environment specifics from the applications and libraries.
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The services provided by the EAL are:
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* DPDK loading and launching
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* Support for multi-process and multi-thread execution types
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* Core affinity/assignment procedures
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* System memory allocation/de-allocation
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* Atomic/lock operations
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* Time reference
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* PCI bus access
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* Trace and debug functions
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* CPU feature identification
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* Interrupt handling
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* Alarm operations
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* Memory management (malloc)
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The EAL is fully described in :ref:`Environment Abstraction Layer <Environment_Abstraction_Layer>`.
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Core Components
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---------------
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The *core components* are a set of libraries that provide all the elements needed
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for high-performance packet processing applications.
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.. _figure_architecture-overview:
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.. figure:: img/architecture-overview.*
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Core Components Architecture
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Ring Manager (librte_ring)
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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The ring structure provides a lockless multi-producer, multi-consumer FIFO API in a finite size table.
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It has some advantages over lockless queues; easier to implement, adapted to bulk operations and faster.
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A ring is used by the :ref:`Memory Pool Manager (librte_mempool) <Mempool_Library>`
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and may be used as a general communication mechanism between cores
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and/or execution blocks connected together on a logical core.
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This ring buffer and its usage are fully described in :ref:`Ring Library <Ring_Library>`.
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Memory Pool Manager (librte_mempool)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The Memory Pool Manager is responsible for allocating pools of objects in memory.
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A pool is identified by name and uses a ring to store free objects.
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It provides some other optional services,
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such as a per-core object cache and an alignment helper to ensure that objects are padded to spread them equally on all RAM channels.
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This memory pool allocator is described in :ref:`Mempool Library <Mempool_Library>`.
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Network Packet Buffer Management (librte_mbuf)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The mbuf library provides the facility to create and destroy buffers
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that may be used by the DPDK application to store message buffers.
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The message buffers are created at startup time and stored in a mempool, using the DPDK mempool library.
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This library provides an API to allocate/free mbufs, manipulate
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packet buffers which are used to carry network packets.
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Network Packet Buffer Management is described in :ref:`Mbuf Library <Mbuf_Library>`.
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Timer Manager (librte_timer)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This library provides a timer service to DPDK execution units,
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providing the ability to execute a function asynchronously.
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It can be periodic function calls, or just a one-shot call.
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It uses the timer interface provided by the Environment Abstraction Layer (EAL)
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to get a precise time reference and can be initiated on a per-core basis as required.
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The library documentation is available in :ref:`Timer Library <Timer_Library>`.
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Ethernet* Poll Mode Driver Architecture
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---------------------------------------
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The DPDK includes Poll Mode Drivers (PMDs) for 1 GbE, 10 GbE and 40GbE, and para virtualized virtio
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Ethernet controllers which are designed to work without asynchronous, interrupt-based signaling mechanisms.
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See :ref:`Poll Mode Driver <Poll_Mode_Driver>`.
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Packet Forwarding Algorithm Support
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-----------------------------------
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The DPDK includes Hash (librte_hash) and Longest Prefix Match (LPM,librte_lpm)
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libraries to support the corresponding packet forwarding algorithms.
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See :ref:`Hash Library <Hash_Library>` and :ref:`LPM Library <LPM_Library>` for more information.
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librte_net
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----------
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The librte_net library is a collection of IP protocol definitions and convenience macros.
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It is based on code from the FreeBSD* IP stack and contains protocol numbers (for use in IP headers),
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IP-related macros, IPv4/IPv6 header structures and TCP, UDP and SCTP header structures.
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