Messages in this thread | | | Date | Sun, 13 Jul 1997 22:02:52 +0200 (CEST) | From | Felix Schroeter <> | Subject | Re: > 1GB physical on x86: Summary so far |
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Hello!
In article <5l90zjv417.fsf@tequila.systemsz.cs.yale.edu> you write: >Felix Schroeter <felix@mamba.pond.sub.org> writes: >> Does that mean, if you have a 1GB real mem machine, there's 1GB of virtual >> memory already used for a permanent mapping of the real 1GB of memory?
>Exactly. >But it's really not a big deal since it's only "virtual memory" >which only costs a few page-table entries (and no swap).
It costs 1GB/1024 = 1MB for the PTEs. And it causes that no user processes can ever have more than 3GB of VM (in fact a bit less, because the kernel needs its own VM in addition to the physmem mapping). On systems without such a permanent mapping, you had a bit less than 4 GB for the VM.
Regards, Felix.
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