How FreeBSD manage more than 4GB on 32 bits architecture

Adrian Chadd adrian at
Fri Apr 10 19:16:51 UTC 2015


Everyone - this is a research project. If they want to hack around
with FreeBSD on a PAE style 32 bit system but massively parallel,
please let them. If they hit the same walls as others have hit, hey,
great. But they may come up with something novel.

Pierre - thanks for looking into it. Yes, there's PAE support in
FreeBSD. Yes, there's some NUMA domain awareness in FreeBSD. You're
definitely not starting from scratch. I don't know of any PAE style
awareness in the MIPS32 code; that would be a good place to start

So please take a look at what PAE / i386 is doing and see if you can
map that to vm and pmap management for MIPS32. It'd likely overlap a
lot with how we would support > 256MB of RAM on MIPS32 - right now we
just use the direct map setup for everything, and that's limited to
the KSEG sizes of 256MB.


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