On Sat, 3 Jun 2000, Andrew Sharp wrote:
> Implementing hot plug CPUs is relatively easy [as long as the user doesn't
> try and idle out ALL the processors ~:^) ].
Easy enough to test for - or should we give the users enough rope to shoot
themselves in both feet at once? :)
> Implementing hot plug memory boards is a different story.
It shouldn't be all that harder. Harder than killing a CPU, certainly, but
far from impossible. Mark the range as unavailable, then page out any user
pages from that region. Most kernel pages could just be moved elsewhere;
the big problem will be devices using buffers for DMA. Presumably the best
way to solve that would be either to reinitialise that driver (rmmod,
insmod) or to have a way to tell the driver to perform the move itself.
Except for reinitialising the drivers, the only impact should be a
performace hit while the memory contents are moved. With the right driver
modifications, we could avoid any actual loss of functionality during the
transition.
This is, IMHO, quite an attractive idea: a fully hot-swappable system,
where any failed component can be replaced without any downtime.
James.
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