Lazy and Speculative Execution

15 January 2007

Lampson: Lazy and Speculative Execution

Lazy: Redo Logging

nFor fault-tolerant persistent state

oPersistent state plus log represents current state

oOnly use the log after a failure

nps = persistent state, l = log, s = state

os = ps; l

oTo apply an update u: l := l; u writing a redo program

oTo install an update u: ps := ps; u

oNeed s' = s, so ps; u; l = ps; l

ou; l = l is sufficient

nThe bet: No crash. An easy win

nRep: state = persistent state + log