COMMON%20INTERFACE%20FOR%20EMBEDDED%20SOFTWARE%20CONFIGURATION

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• Expensive hardware increases overall cost.
• Lesser degree of scalability.
• Most of the visible hardware is required to
  control the invisible hardware or software.

Purchased in 1970 by UNT, the IBM 360/50 CPU was
acquired to support academic and administrative
computing. The original configuration of the
360/50 was one multiplexer channel, one selector
channel, 256K core memory, a 1403 line printer, a
2540 card reader/punch, three 30KB tape drives,
and five 2314 single density disk drives. The
original operating system was OS/MFT/HASP
supporting a maximum of three user partitions.
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• With the help of one web server and several web
  pages per software, we can configure all hardware
  and software at no extra hardware cost.
• Very high degree of scalability.

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Common Gateway Interface (CGI)

• CGI as a separate process hampers optimization
  goals static resources (PCB), run-time resource
  (context switching time).
• Several web pages of several different software
  and hardware and their corresponding CGI
  executables make management clumsy, wastage of
  file-system space.

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Solutions to CGI drawbacks

• Fast CGI
• Intelligent approach to save spawning of separate
  process PER request.
• Similar kind of requests are serviced by one
  process each.
• The process keeps running listening for other
  such requests.
• Wastage of resources.
• Ad hoc intelligence reduces scalability

• In-process CGI
• Once a CGI process is spawned, it converts all
  function calls into inline functions.
• Reduces the overhead of function calls.
• Greater image size because of inline functions.
• It still spawns a separate process per request.

• CGI threads
• Spawn a separate THREAD instead of Process.
• Spawning of threads still incurs context
  switching.
• For Linux, threads and processes are one and the
  same at kernel-level.

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My approach of CGI

• CGI as function call
• Instead of spawning process or thread, if CGI can
  be called as a function, it would save enormous
  amount of resources.

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Advantages of CGI Function

• No spawning of process, no context switching.
• Saves memory and other critical resources,
  improves overall speed and performance.
• No inline functions involved, maintaining small
  web server footprint.
• Same interface with web server as normal CGI
  process.
• Migration from CGI process to CGI function is
  easy.

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Drawbacks of CGI Function

• Allows code isolation but NO execution isolation
  from web server. If CGI function crashes, whole
  web server crashes.
• Sequential execution so the web server has to
  wait for the CGI function to finish.

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Future Extensions
Questions Please!!!

• Universal file manipulation library
• XML parsing tool.
• Configuration on the fly
• Software restarts to read from configuration file
  , entails Unaffordable downtime.
• Software should export functions that are
  dynamically linked with web server.
• These functions change the variable values on the
  fly.