Project ForgeFor 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.
- AIV only
- BI and IV only
- I, III and IV only
- DI, II, III and IV
Explanation
The classic (Baer-Wang) necessary conditions for the multilevel inclusion property are: L2 must be at least as large as L1 (IV), L2's associativity must be at least as high as L1's (III), and — in the standard simplified treatment — L1 is assumed to be write-through so that L2 always has an up-to-date copy without extra invalidation protocol overhead (I). L2's own write policy (II) is not a requirement for inclusion.
Source: GATE CS 2008 (2008)
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