For every 4 bytes for storing a thread's calculation, 60 bytes is empty padding. This empty space rapidly increases rapidly as the number of threads increases.

This is what we wanted, but this is incredibly inefficient. The whole point of the cache is to improve performance by contain relevant data to minimize cache misses. In practice, a processor will likely be juggling other threads with their own data that may or may not be related to this program. By padding out the cache line, we are forcing cache misses to occur.