Address Collision using i386 4G/4G Memory Split

[Alexander Lochmann]

Hi folks!

According to git commit e3089a (https://reviews.freebsd.org/D1463)
FreeBSD 12.0 i386 uses separate address spaces for kernel and user
space. So basically two memory areas, one in each space, can have the
same address.
Is this possible with FreeBSD 12.0? Is this likely to happen?

On my opinion, this is also very expensive in terms of performance.
Any copy{in,out} has to flush the TLB.
(http://fxr.watson.org/fxr/source/i386/i386/copyout_fast.s#L91)
Why are you still using this 4G/4G approach?

Regards,
Alex

-- 
Technische Universität Dortmund
Alexander Lochmann                PGP key: 0xBC3EF6FD
Otto-Hahn-Str. 16                 phone:  +49.231.7556141
D-44227 Dortmund                  fax:    +49.231.7556116
http://ess.cs.tu-dortmund.de/Staff/al

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