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Suppose in speed-critical code we have a pair of arrays that are frequently used together, where the exact size doesn't matter, it just needs to be set to something reasonable, e.g.
int a[256], b[256];
Is this potentially a pessimization because the low address bits being the same can make it harder for the cache to handle both arrays simultaneously? Would it be better to specify e.g. 300 instead of 256?