dfdb6edd3f
This patch adds getting started guide for SPDK vhost. This document describes how to build and run vhost application. Signed-off-by: Piotr Pelplinski <piotr.pelplinski@intel.com> Signed-off-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com> Change-Id: Icab3ad75f1ebf4d53153fb7070151a7244f1dfa9
123 lines
5.1 KiB
Markdown
123 lines
5.1 KiB
Markdown
# SPDK Directory Structure {#directory_structure}
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# Overview {#dir_overview}
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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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## Applications {#dir_app}
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The `app` top-level directory contains four applications:
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- `app/iscsi_tgt`: An iSCSI target
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- `app/nvmf_tgt`: An NVMe-oF target
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- `app/iscsi_top`: Informational tool (like `top`) that tracks activity in the
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iSCSI target.
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- `app/trace`: A tool for processing trace points output from the iSCSI and
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NVMe-oF targets.
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- `app/vhost`: A vhost application that presents virtio controllers to
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QEMU-based VMs and process I/O submitted to those controllers.
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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 `etc/spdk` directory.
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## Build Collateral {#dir_build}
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The `build` directory contains all of the static libraries constructed during
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the build process. The `lib` directory combined with the `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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## 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 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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- `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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## 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`.
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### Block Device Abstraction Layer {#dir_bdev}
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The `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 `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 `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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### Configuration File Parser {#dir_conf}
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The `conf` directory contains configuration file parser. The public header
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is `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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## Makefile Fragments {#dir_mk}
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The `mk` directory contains a number of shared Makefile fragments used in the build 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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