3 ms·

And even if it was an instruction for every access, memory access is much more expensive than and add (at least nowadays -- I don't know if that's always been t

• dahart 4y ago
  Similarly I like to think about it as the add/subtract instruction is very small compared to malloc (and maybe could be included in a custom allocator for free). So the one extra instruction will always be somewhere between relatively minor to negligible and unnoticed. Yeah today memory access on a cache miss is really expensive. I think memory was normally running at a different clock rate than the CPU even 50-60 years ago, so has always been something where you can’t touch memory every instruction. The latency of a cache miss wasn’t nearly as bad in the past. When the data cache was invented, a main memory access was like 4 times slower than register access. Today, main memory access can be more than a hundred time slower, sometimes it can approach a thousand times slower, which is why we always have multi-level caches now. And memory latency is still getting worse. If someone figured out how to make memory faster without increasing the cost or the energy consumption, they’d be rich! ;)