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Hi Alan.
>> I've been able to find very little information regarding this
>> topic, other than the comments in include/asm-i386/page.h. I was
>> hoping you could point me towards a resource that might answer the
>> following questions:
>> 1. How is __PAGE_OFFSET actually used? The page.h comments aren't
>> clear on this. They suggest *how* to change the value, but not
>> *why*.
> There is a big problem with the x86 architecture. Unless you start
> messing around switching page tables all the time (which isnt
> cheap) you can't easily access more than 4Gig combined
> physical+virtual address space.
> __PAGE_OFFSET is the dividing line. By default its 3Gig virt 1Gig
> phys. If you set it to 2/2 or 1/3 you get more physical ram but
> less virtual space per process.
Perhaps the enclosed patch (against 2.1.131ac13) would come in useful
here. It basically adds a configuration option in "Processor type and
features" to select the breakpoint between physical RAM and virtual
memory, and the method used allows quarter-gigabyte steps to be
selected. I've listed all valid steps from 0.75 to 3.00 Gigs of RAM,
but that can obviously be changed to suit...
Test results and comments much appreciated...
Best wishes from Riley.
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