No, the wastage is due to because I'm not accessing data in a "linear" fashion if I lay out the matrices naively (actually pulling n by n square submatrices from the big matrix), and prefetcher brings in data with its baked in locality rules, but its assumptions doesn't fit my access pattern. So 20 percent of the data is thrown away.

If I change how I fill and lay my matrices out, I can align my data with how prefetcher assumes, and way less data will be trashed during the process.

I didn't do that because it needed a codebase-wide refactorization, and my code was already 30x faster than reference implementation with better accuracy, so we didn't pursue that avenue.