By context switching overhead, I assume you mean the overhead of faulting data into the cache from a thread that had been sleeping. Evented systems have this overhead too when switching between events related to different requests.
Stack size I've discussed in another response. It can and should be decreased if you plan on working with a lot of threads.
I can't comment on the Mac OS X scheduler. The Linux scheduler handles it just fine, and my understanding is that the Windows one does OK with it too.
The small amount of kernel memory that isn't swappable likely isn't your system's overall throughput constraint, but if it is I stand corrected.
Stack size I've discussed in another response. It can and should be decreased if you plan on working with a lot of threads.
I can't comment on the Mac OS X scheduler. The Linux scheduler handles it just fine, and my understanding is that the Windows one does OK with it too.
The small amount of kernel memory that isn't swappable likely isn't your system's overall throughput constraint, but if it is I stand corrected.