Re: [PATCH v35 1/5] mm: support to get hints of free page blocks

[Wei Wang <wei.w.wang@intel.com>]

On 07/12/2018 10:30 AM, Linus Torvalds wrote:
> On Wed, Jul 11, 2018 at 7:17 PM Wei Wang <wei.w.wang@intel.com> wrote:
> > Would it be better to remove __GFP_THISNODE? We actually want to get all
> > the guest free pages (from all the nodes).
> Maybe. Or maybe it would be better to have the memory balloon logic be
> per-node? Maybe you don't want to remove too much memory from one
> node? I think it's one of those "play with it" things.
>
> I don't think that's the big issue, actually. I think the real issue
> is how to react quickly and gracefully to "oops, I'm trying to give
> memory away, but now the guest wants it back" while you're in the
> middle of trying to create that 2TB list of pages.

OK. virtio-balloon has already registered an oom notifier 
(virtballoon_oom_notify). I plan to add some control there. If oom happens,
- stop the page allocation;
- immediately give back the allocated pages to mm.

Best,
Wei