15 January 2007
Lampson: Lazy and Speculative Execution
24
Speculative: Data Speculation
nGeneralize
from branch prediction: predict data
oSeems implausible in general—predict 0?
oWorks well to predict that cached data is still valid
▬Even though it might be updated by a concurrent
process
nThe
bet: Data will turn out as predicted
oAn easy win for coherent caches
nWorks
for distributed file systems too
oVariation: speculate that sync
will succeed
▬Block output that depends on success