For inclusion to hold between two cache levels L1 and L2 in a multi-level cache hierarchy, which of the following are necessary?
I. L1 must be a write-through cache II. L2 must be a write-through cache III. The associativity of L2 must be greater than that of L1 IV. The L2 cache must be at least as large as the L1 cache
(A) IV only
(B) I and IV only
(C) I, III and IV only
(D) I, II, III and IV
Explanation: Statement I is not necessary because at the same point of time, data need not to be exactly same. Therefore, write back policy can also be used.
Statement II is not necessary when when discussing only about L1 and L2.
Statement III is not necessary because associativity can be equal.
Statement IV is necessary, The L2 cache must be at least as large as the L1 cache.
So, option (A) is correct.