> Thread switch time does not scale to the # of threads involved. True, but the number of context switches does increase and that in turn decreases the ratio o

> Thread switch time does not scale to the # of threads involved. True, but the number of context switches does increase and that in turn decreases the ratio of useful work vs. context switch overhead. Also the secondary costs of context switching, like flushing caches increase. If there are hundreds of threads, the chances that a thread is woken up with warm caches decreases.