30af9d3798
This has been on the TODO list for a long time Change-Id: Ibdd130f976e9f4436a9dc94919878e2ff187e873 Signed-off-by: Ben Walker <benjamin.walker@intel.com> Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/453452 Tested-by: SPDK CI Jenkins <sys_sgci@intel.com> Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com> Reviewed-by: Jim Harris <james.r.harris@intel.com>
103 lines
4.4 KiB
Markdown
103 lines
4.4 KiB
Markdown
# SPDK Structural Overview {#overview}
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# Overview {#dir_overview}
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SPDK is composed of a set of C libraries residing in `lib` with public interface
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header files in `include/spdk`, plus a set of applications built out of those
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libraries in `app`. Users can use the C libraries in their software or deploy
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the full SPDK applications.
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SPDK is designed around message passing instead of locking, and most of the SPDK
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libraries make several assumptions about the underlying threading model of the
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application they are embedded into. However, SPDK goes to great lengths to remain
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agnostic to the specific message passing, event, co-routine, or light-weight
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threading framework actually in use. To accomplish this, all SPDK libraries
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interact with an abstraction library in `lib/thread` (public interface at
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`include/spdk/thread.h`). Any framework can initialize the threading abstraction
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and provide callbacks to implement the functionality that the SPDK libraries
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need. For more information on this abstraction, see @ref concurrency.
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SPDK is built on top of POSIX for most operations. To make porting to non-POSIX
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environments easier, all POSIX headers are isolated into
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`include/spdk/stdinc.h`. However, SPDK requires a number of operations that
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POSIX does not provide, such as enumerating the PCI devices on the system or
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allocating memory that is safe for DMA. These additional operations are all
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abstracted in a library called `env` whose public header is at
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`include/spdk/env.h`. By default, SPDK implements the `env` interface using a
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library based on DPDK. However, that implementation can be swapped out. See @ref
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porting for additional information.
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## Applications {#dir_app}
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The `app` top-level directory contains full-fledged applications, built out of the SPDK
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components. For a full overview, see @ref app_overview.
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SPDK applications can typically be started with a small number of configuration
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options. Full configuration of the applications is then performed using
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JSON-RPC. See @ref jsonrpc for additional information.
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## Libraries {#dir_lib}
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The `lib` directory contains the real heart of SPDK. Each component is a C library with
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its own directory under `lib`. Some of the key libraries are:
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- @ref bdev
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- @ref nvme
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## Documentation {#dir_doc}
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The `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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## Examples {#dir_examples}
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The `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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`examples/nvme/hello_world`.
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## Include {#dir_include}
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The `include` directory is where all of the header files are located. The public API
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is all placed in the `spdk` subdirectory of `include` and we highly
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recommend that applications set their include path to the top level `include`
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directory and include the headers by prefixing `spdk/` like this:
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~~~{.c}
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#include "spdk/nvme.h"
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~~~
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Most of the headers here correspond with a library in the `lib` directory. There
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are a few headers that stand alone, however. They are:
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- `assert.h`
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- `barrier.h`
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- `endian.h`
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- `fd.h`
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- `mmio.h`
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- `queue.h` and `queue_extras.h`
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- `string.h`
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There is also an `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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## Scripts {#dir_scripts}
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The `scripts` directory contains convenient scripts for a number of operations. The two most
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important are `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 `setup.sh` which binds and unbinds devices
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from kernel drivers.
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## Tests {#dir_tests}
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The `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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