doc: Begin documenting the directory structure
This adds a document that begins to describe the SPDK repository directory structure. Much of the document still needs to be written. Change-Id: I8bb6659e5e3e9a22e6bc2d3374d41b16a51614f8 Signed-off-by: Ben Walker <benjamin.walker@intel.com>
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@ -760,6 +760,7 @@ WARN_LOGFILE =
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INPUT = ../include/spdk \
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mainpage.txt \
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directory_structure.txt \
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ioat/index.txt \
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nvme/index.txt \
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nvme/async_completion.txt \
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doc/directory_structure.txt
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doc/directory_structure.txt
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/*-
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* BSD LICENSE
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*
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* Copyright (c) Intel Corporation.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* * Neither the name of Intel Corporation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/**
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\page directory_structure SPDK Directory Structure
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SPDK is primarily a collection of C libraries intended to be consumed directly by
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applications, but the repository also contains many examples and full-fledged applications.
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This will provide a general overview of what is where in the repository.
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\section dir_app Applications
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The \c app top-level directory contains four applications:
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- \c app/iscsi_tgt: An iSCSI target
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- \c app/nvmf_tgt: An NVMe-oF target
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- \c app/iscsi_top: Informational tool (like \c top) that tracks activity in the
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iSCSI target.
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- \c app/trace: A tool for processing trace points output from the iSCSI and
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NVMe-oF targets.
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The application binaries will be in their respective directories after compiling and all
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can be run with no arguments to print out their command line arguments. For the iSCSI
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and NVMe-oF targets, they both need a configuration file (-c option). Fully commented
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examples of the configuration files live in the \c etc/spdk directory.
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\section dir_build Build Collateral
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The \c build directory contains all of the static libraries constructed during
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the build process. The \c lib directory combined with the \c include/spdk
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directory are the official outputs of an SPDK release, if it were to be packaged.
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\section dir_doc Documentation
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The \c doc top-level directory contains all of SPDK's documentation. API Documentation
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is created using Doxygen directly from the code, but more general articles and longer
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explanations reside in this directory, as well as the Doxygen config file.
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To build the documentation, just type `make` within the doc directory.
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\section dir_examples Examples
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The \c examples top-level directory contains a set of examples intended to be used
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for reference. These are different than the applications, which are doing a "real"
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task that could reasonably be deployed. The examples are instead either heavily
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contrived to demonstrate some facet of SPDK, or aren't considered complete enough
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to warrant tagging them as a full blown SPDK application.
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This is a great place to learn about how SPDK works. In particular, check out
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\c examples/nvme/hello_world.
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\section dir_include Include
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The \c include directory is where all of the header files are located. The public API
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is all placed in the \c spdk subdirectory of \c include and we highly
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recommend that applications set their include path to the top level \c include
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directory and include the headers by prefixing \c spdk/ like this:
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\code #include "spdk/nvme.h" \endcode
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Most of the headers here correspond with a library in the \c lib directory and will be
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covered in that section. There are a few headers that stand alone, however. They are:
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- \c assert.h
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- \c barrier.h
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- \c endian.h
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- \c fd.h
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- \c mmio.h
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- \c queue.h and \c queue_extras.h
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- \c string.h
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There is also an \c spdk_internal directory that contains header files widely included
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by libraries within SPDK, but that are not part of the public API and would not be
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installed on a user's system.
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\section dir_lib Libraries
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The \c lib directory contains the real heart of SPDK. Each component is a C library with
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its own directory under \c lib.
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\subsection dir_bdev Block Device Abstraction Layer
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The \c bdev directory contains a block device abstraction layer that is currently used
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within the iSCSI and NVMe-oF targets. The public interface is \c include/spdk/bdev.h.
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This library lacks clearly defined responsibilities as of this writing and instead does a
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number of
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things:
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- Translates from a common \c block protocol to specific protocols like NVMe or to system
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calls like libaio. There are currently three block device backend modules that can be
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plugged in - libaio, SPDK NVMe, CephRBD, and a RAM-based backend called malloc.
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- Provides a mechanism for composing virtual block devices from physical devices (to do
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RAID and the like).
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- Handles some memory allocation for data buffers.
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This layer also could be made to do I/O queueing or splitting in a general way. We're open
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to design ideas and discussion here.
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\subsection dir_conf Configuration File Parser
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The \c conf directory contains configuration file parser. The public header
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is \c include/spdk/conf.h. The configuration file format is kind of like INI,
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except that the directives are are "Name Value" instead of "Name = Value". This is
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the configuration format for both the iSCSI and NVMe-oF targets.
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... Lots more libraries that need to be described ...
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\section dir_mk Makefile Fragments
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The \c mk directory contains a number of shared Makefile fragments used in the build system.
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\section dir_scripts Scripts
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The \c scripts directory contains convenient scripts for a number of operations. The two most
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important are \c check_format.sh, which will use astyle and pep8 to check C, C++, and Python
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coding style against our defined conventions, and \c setup.sh which binds and unbinds devices
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from kernel drivers.
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\section dir_tests Tests
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The \c test directory contains all of the tests for SPDK's components and the subdirectories mirror
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the structure of the entire repository. The tests are a mixture of unit tests and functional tests.
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*/
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@ -46,6 +46,10 @@ It achieves high performance by moving all of the necessary drivers
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into userspace and operating in a polled mode instead of relying on interrupts,
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which avoids kernel context switches and eliminates interrupt handling overhead.
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\section general General Information
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- \ref directory_structure
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\section modules Modules
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- \ref nvme
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