Re: [PATCH 2/2] KVM: Scalable memslots implementation

[David Hildenbrand]

On 03.02.21 14:46, Paolo Bonzini wrote:
> On 03/02/21 14:44, David Hildenbrand wrote:
> > BTW: what are your thoughts regarding converting the rmap array on
> > x86-64 into some dynamic datastructre (xarray etc)? Has that already
> > been discussed?
>
> Hasn't been discussed---as always, showing the code would be the best
> way to start a discussion. :)

If only a workday would have more hours :)

> However, note that the TDP MMU does not need an rmap at all.  Since that
> one is getting ready to become the default, the benefits of working on
> the rmap would be quite small and only affect nested virtualization.

Right, but we currently always have to allocate it.

8 bytes per 4k page, 8 bytes per 2M page, 8 bytes per 1G page.

The 4k part alone is 0.2% of the memblock size.

For a 1 TB memslot we might "waste" > 2 GB on rmap arrays.

(that's why I am asking :) )

--
Thanks,

David / dhildenb