On Fri 13-04-18 16:01:43, David Hildenbrand wrote:
> On 13.04.2018 15:44, Michal Hocko wrote:
> > [If you choose to not CC the same set of people on all patches - which
> > is sometimes a legit thing to do - then please cc them to the cover
> > letter at least.]
> >
> > On Fri 13-04-18 15:16:24, David Hildenbrand wrote:
> >> I am right now working on a paravirtualized memory device ("virtio-mem").
> >> These devices control a memory region and the amount of memory available
> >> via it. Memory will not be indicated via ACPI and friends, the device
> >> driver is responsible for it.
> >
> > How does this compare to other ballooning solutions? And why your driver
> > cannot simply use the existing sections and maintain subsections on top?
> >
>
> (further down in this mail is a small paragraph about that)
Sorry, I just stopped right there and didn't even finsh to the end.
Shame on me! I will do my homework and read it carefully (next week).
[...]
> "And why your driver cannot simply use the existing sections and
> maintain subsections on top?"
>
> Can you elaborate how that is going to work? What I do as of now, is to
> remember for each memory block (basically a section because I want to
> make it as small as possible) which chunks ("subsections") are
> online/offline. This works just fine. Is this what you are referring to?
Well, basically yes. I meant to suggest you simply mark pages reserved
and pull them out. You can reuse some parts of such a struct page for
your metadata because we should simply ignore those.
You still have to allocate memmap for the full section but 128MB
sections have a nice effect that they fit into a single PMD for
sparse-vmemmap. So you do not really need to touch mem sections, all you
need is to keep your metadata on top.
--
Michal Hocko
SUSE Labs
