I've done a lot of work on similar topics, building real-time messaging systems in C++. The author's findings are not unique and are very common to any producer

I've done a lot of work on similar topics, building real-time messaging systems in C++. The author's findings are not unique and are very common to any producer-consumer messaging system. Essentially the issue is that you want your L2 to stay hot. If a single core is enough to satisfy your processing requirements, adding more threads and more cores isn't going to speed you up. Instead the parallelism will actually put more pressure on the scheduler, causing your threads to bounce around to cores with a cold L2 cache. If your cache is cold, your pipeline stalls out, and your performance is dead.