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apadwekar

Invalidate has a higher miss rate than update because useful cache lines get dropped when other caches enter the exclusive state, whereas the cache lines are retained in the update case.

firebb

From 213, we learn three kinds of cache misses: Cold miss, Capacity miss and Conflict miss. Here we learn the fourth kind of cache miss due to cache invalidation and it can be triggered by true/false sharing.

o_o

Update is not necessarily better. It looks like it is better because updating makes sure there aren't as many misses, since the most recent data is in the cache. But, in update the cache will always want to be full, which leads to updates having to be communicated across the processors, which can be expensive.