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-space1.

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


See also

References

  • ^1 CITI_TR_00-4
  • High-Performance Memory-Based Web Servers: Kernel and User-Space Performance. Philippe Joubert, Robert B. King, Rich Neves, Mark Russinovich, John M. Tracey. IBM. T. J. Watson Research Center