Cross-platform implementations

These implementations are shared by several platforms, each in a directory of its own under lib/backend/. For example, instead of the Linux, FreeBSD, and macOS platforms each implementing POSIX asynchronous I/O, lib/backend/posix provides it once, and they all include it in their backend configs.

Similarly, xNVMe provides several software-only implementations of the xNVMe API, such as lib/backend/thrpool, which implements the asynchronous parts of the xNVMe API with a thread pool, and lib/backend/emu and lib/backend/nil.

Each platform combines these with its own implementations into predefined backend configs (xnvme_be_config), providing tested and validated combinations. In addition, lib/backend/ramdisk provides simple device emulation, and lib/backend/shim emulates the NVMe admin commands for regular files.

Instrumentation

• Memory Allocators

  • posix, Use libc malloc()/free() with sysconf() for alignment

• Asynchronous Interfaces

  • nil, xNVMe null-IO, does nothing but complete submitted commands, for experimentation only to evaluate xNVMe encapsulation overhead

  • emu, ..

  • thrpool, ..

  • posix, ..

• Synchronous Interfaces

  • psync, Use pread()/write() for synchronous I/O