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  • When process in memory, no disk space allocated to it
  • However, when a need for swapping occurs, suitable disk space must be found
  • Area on disk where this happens : swap space (usually the /tmp area in unix)
  • Sometimes, swap space automatically allocated on process creation (hence, a fixed swap space per process)
  • An average process in the middle of memory (after system has reached equilibrium) will encounter half allocations and half deallocations (above and below)
  • The Fifty percent rule = if mean number of processes in memory is n, the mean number of holes is n/2
  • Thats because adjacent holes are merged, adjacent processes are not (hence a process / hole asymmetry) - just a heuristic
  • Numerous others, used for optimising swapping performance

    Omer F Rana
    Tue Feb 11 19:21:10 GMT 1997