> > I know that SunOS OpenServer can support up to 4GB memory though
> > it is very expensive. How do they manage to do that?
>
> You have to start flushing the TLB every time you enter kernel mode and
> need to touch a physical memory object as opposed to kernels own data/bss
> space. It could be added to Linux but 4Gb boxes arent the norm and there
> is a performance hit for a kernel built that way.
I think we can actually support 'mini-user-space virtual memory' setups,
eg a 3.5G+0.5G kernel/user split [i think David mentioned such Sparc
setups months ago]. Eg. a big ISP's login server or whatever, where
individual process virtual memory size is not an issue (or can be
distributed between processes easily).
then there is the issue of 4G+ boxes, thats only hard if such memory will
truly be PCI DMA-able (how? even PCI bus offsets are 32 bits, aint they?)
So if there will be such a RL box, it will be handicapped anyway?
-- mingo