In-kernel web server

An in-kernel web server is an unlimited HTTP server that runs in kernel space or equivalent. It is also called "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: aka Network Cache and Accelerator (NCA) kernel module
• HP-UX:
• Linux: TUX
• Mesibo In-kernel real-time messaging server
• Windows NT: (part of IIS)
• SPIN:
• OpenVMS:

See also[]

• Comparison of web server software
• Service-oriented architecture
• Unikernel/Exokernel (eg. SPIN's loadable kernel modules)

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