[CSE]  Advanced Operating Systems 
  COMP9242 2002/S2  		UNSW
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Next: Fpage Notes Up: 01-l4 Previous: Fpage Mapping Examples

Formal Fpage Mapping Rules

  • Sender specifies fpage as \(b\), \(s\): fpage \([b\times2^s, (b+1)\times2^s]\),
  • Sender specifies hotspot \(h\),
  • Receiver specifies fpage as \(b'\), \(s'\): fpage \([{b'}\times2^{s'}, ({b'}+1)\times2^{s'}]\).

    \(s=s'\):
    mapping is \(b\times2^s \mapsto b'\times2^s\)
    hot spot specification is not needed
    \(s<s'\):
    mapping is \(b\times2^s \mapsto {b'}_{[63,s']} h_{[s'-1,s]} 0_{(s)}\)
    sender's fpage is aligned around hot spot
    \(s>s'\):
    mapping is \({b}_{[63,s]} h_{[s-1,s']} 0_{(s')} \mapsto b'\times2^{s'}\)
    receiver's fpage is aligned around hot spot

Note: The actual value of \(h\) is not important, only \(\relax h \bmod \max (2^s, 2^{s'})\).

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Gernot Heiser 2002-08-07