In-kernel web server

An in-kernel web server is an unlimited HTTP server that runs in kernel space or equivalent. It is also known as "accelerator".

Benefits

 * Performance: the path taken by data from a source device (i.e. a disk) to a destination device (i.e. a NIC). Proper asynchronous zero-copy interfaces would make this available from user-space.
 * Scalability: with respect to number of simultaneous clients. Event notification of comparable scalability seems unlikely in user-space.

Drawbacks

 * Security: Kernel processes run with unlimited privileges.
 * Portability. Every kernel needs a specific implementation route.
 * Reliability. Failure in the webserver may crash the OS.

Implementations

 * illumos/Solaris: NCAkmod aka Network Cache and Accelerator (NCA) kernel module
 * HP-UX: NSAhttp (NSA is an acronym for Network Server Accelerator)
 * Linux: TUX
 * Mesibo In-kernel real-time messaging server
 * Windows NT: http.sys (part of IIS)
 * SPIN: http
 * OpenVMS: WASD.trap