I did `sudo nvram boot-args="-no_shared_cr3"`, and I think I see the (seemingly minor, at this point) performance hit. There's an explanatory comment in http://

I did `sudo nvram boot-args="-no_shared_cr3"`, and I think I see the (seemingly minor, at this point) performance hit. There's an explanatory comment in http://opensource.apple.com/source/xnu/xnu-2782.1.97/osfmk/x86_64/copyio.c http://opensource.apple.com/source/xnu/xnu-2782.1.97/osfmk/x... that seems to explain the feature, though not in detail.