多线程缓存未命中利用

Question

When I eg. iterate over a linked list and become really unlucky, I will have ~ 0% cache-hitrate (let's assume this anyways). Let's also assume I have a CPU that can only run one Instruction at a time (no multicore / hyperthreads) for simplicity. Cool. Now with my 0% hitrate the CPU / program is spending 99% of the time waiting for data.

Question : If a thread is waiting for data from the RAM / disk is that core blocked? Or can I exploit the low cache-hitrate by running other threads (or another way that is not todo with increasing the hitrate) to not have the CPU exclusively wait for data and do other work instead?

Answer 1

If you run SMT, then the other thread can grap all the core resources and hence cover over the cache miss (at least partially).

I know of no processor that makes task switch on cache miss, but I know several architectures that use SMT-2/4/8 (yes some Power CPU's have SMT-8) to cover over such cases.