Re: 2G memory split

[Alan Cox]

On Maw, 2006-01-10 at 09:56 -0700, Jeff V. Merkey wrote:
> RH ES uses 4:4 which is ideal and superior to this hack.

Its a non trivial trade-off. 4/4 lets you run very large physical memory
systems much more efficiently than usual but you pay a cost on syscalls
and some other events when using the majority of processors. The 4/4
tricks also give most emulations (eg Qemu) serious heartburn trying to
emulate %cr3 reloading via mmap and other interfaces with high overhead
in relative terms.

Of course AMD64 kind of shot the problem in the head once and for all.

Alan

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