Re: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19

Rob Landley
2005-11-03T00:10:27Z

On Wednesday 02 November 2005 09:02, Gerrit Huizenga wrote:
> > but that's obviously not 'generic unpluggable kernel RAM'. It's very
> > special RAM: RAM that is free or easily freeable. I never argued that
> > such RAM is not returnable to the hypervisor.
>
> Okay - and 'generic unpluggable kernel RAM' has not been a goal for
> the hypervisor based environments. I believe it is closer to being
> a goal for those machines which want to hot-remove DIMMs or physical
> memory, e.g. those with IA64 machines wishing to remove entire nodes

Keep in mind that just about any virtualized environment might benefit from
being able to tell the parent system "we're not using this ram". I mentioned
UML, and I can also imagine a Linux driver that signals qemu (or even vmware)
to say "this chunk of physical memory isn't currently in use", and even if
they don't actually _free_ it they can call madvise() on it.

Heck, if we have prezeroing of large blocks, telling your emulator to
madvise(ADV_DONTNEED) the pages for you should just plug right in to that
infrastructure...

Rob