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How about a different example entirely? Memory nowadays is either CPU (and the GPU can access it) or GPU (and the CPU has a window into it). It's terribly impor

How about a different example entirely? Memory nowadays is either CPU (and the GPU can access it) or GPU (and the CPU has a window into it). It's terribly important to use the right one: if a chunk of memory is mostly used by the CPU, it needs to be CPU memory, and if it's mostly used by the GPU, it needs to be GPU memory. But there's no good way to specify that. You might argue that a modern computer is more like programming a tightly-bound, nonuniform multi-processor system. And I'd agree. But C doesn't much to help program such a thing.

jstimpfle 8y ago
Still, what you normally do and can assume is that you're using just "CPU" memory with pretty predictable (I think) latencies and a transparent caching layer. When different things are mapped into the address space, that's an abstraction the programmer (or the user) consciously made. It should be possible to figure out the performance characteristics there. Of course, many programs work on various machines with their own performance characteristics. You should still be able optimize for any one of them by querying the hardware and selecting an appropriate implementation. If you want to put in the work. I don't think assembler/C is such a big problem here. But then again, I'm not a low level guy (in this sense) for now.