Re: [Lhms-devel] RE: memory hotremove prototype, take 3

From: Pavel Machek
Date: Thu Dec 04 2003 - 04:55:54 EST


> > > > IMHO, To hot-remove memory, memory attribute should be divided
> > > > into Hotpluggable and no-Hotpluggable, and each attribute memory
> > > > should be allocated each unit(ex. node).
> > >
> > > Why? I still don't get that -- we should be able to use the virtual
> > > addressing mechanism of any CPU to swap under the rug any virtual
> > > address without needing to do anything more than allocate a page frame
> > > for the new physical location
> >
> > My understanding is that the kernel and device drivers sometimes
> > assume physical memory address is not changed.
> > For example, IA32 kernel often uses __PAGE_OFFSET.
> > I suppose that there are many case which the kernel and device drivers
> > assume physical address is not changed like this.
> > Even if we use Mr. Iwamoto's method use, some memories will remain.
> Grrrr ... my concern is that Murphy's Law says that we'll need to hotplug
> the memory that we cannot in most of the cases (pray not). I guess I will
> need to research some more to think how to do it.
> I still think we could use the CPU's virtualization mechanism--of course,
> and as you and Tony Luck mention, we'd had to track down and modify the
> parts that assume physical memory et al. That they use large pages
> or

...which means basically auditing whole kernel, and rewriting half of
drivers. Good luck with _that_.
Horseback riding is like software...
...vgf orggre jura vgf serr.
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