Except that you've just split your available cache region between multiple processes. This can actually decrease performance, I remember cache thrashing back i

Except that you've just split your available cache region between multiple processes. This can actually decrease performance, I remember cache thrashing back in the P4 days that could cause an application like MS Word to take minutes to load. One process evicting data the other one needs and vice versa. It circumstantially makes the situation worse instead of better. Turn off hyper-threading and boom, everything started to function normally. The solution to not having enough food for one mouth often isn't to add another mouth. I still see this in modern benchmarks on modern systems where multicore throughput on many benchmarks is just better when you just turn off SMT. AMD's 3D chips go faster because of the huge cache. Every time we add another process to a core we just split the cache in half instead. Clearly, this is workload dependent. But I immediately turn off SMT on new systems I get. I'm not core limited, I'm usually single thread limited. Like, always. No reason to keep SMT on for this case.