In-kernel web server

Benefits

• Performance. The path taken by data from disk to network. 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 kernel module
• HP-UX: NSAhttp
• Linux: TUX
• In-kernel real-time messaging server
• Windows NT: http.sys
• SPIN: http
• OpenVMS: WASD.trap