I hadn't seen this before (thanks) and haven't been through it, but it's doubtless up to INRIA's usual standards. However, I think "absolute need" is undersell

I hadn't seen this before (thanks) and haven't been through it, but it's doubtless up to INRIA's usual standards. However, I think "absolute need" is underselling the importance. Cache performance can account for factors of several in computational work if you get affinity wrong, and relevant counters are usually in the default initial set for profiling. It's just that what's available is highly hardware-dependent, and finding out what some counters -- especially SIMD ones -- really measure can be a challenge :-(.