"It doesn't matter how fast your language is, you're just racing to get to wait on I/O faster." But it does matter how small your runtime (and inner loops) are

"It doesn't matter how fast your language is, you're just racing to get to wait on I/O faster." But it does matter how small your runtime (and inner loops) are, if you want to live in the L1 and L2 cache and avoid paying the RAM latency penalty.