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SubjectRe: [PATCH] CPU hot swap for 2.4.3 + s390 support
On Sun, 6 May 2001, Chris Wedgwood wrote:
> On Sat, May 05, 2001 at 10:43:27AM -0400, Peter Rival wrote:
>
> Has anyone looked into memory hot swap/hot add support?
>
> Adding memory probably isn't going to be too hard... but taking
> existing memory off line is tricky. You have to find some way of
> finding all the pages that are in use and then dealing with them
> appropriately, and when some are locked or contain kernel data this
> would be extremely difficult I should think.

Actually:

1. the kernel uses virtual memory itself and accesses its
data structures through page tables
2. reverse mapping stuff is easy (though it costs 8 bytes
of overhead per mapped pte, probably doubling page table
overhead)

This only leaves two issues, the first is device drivers and
the second is the question whether we'd want the overhead
needed to implement the (fairly easy) memory relocation.

regards,

Rik
--
Virtual memory is like a game you can't win;
However, without VM there's truly nothing to lose...

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