Re: [PATCH v2 0/5] KVM: mm: count KVM page table pages in pagetable stats

[Yosry Ahmed]

+Johannes Weiner  +Michal Hocko  +Roman Gushchin

On Tue, Apr 5, 2022 at 11:45 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> On Mon, Apr 04, 2022, Yosry Ahmed wrote:
> > We keep track of several kernel memory stats (total kernel memory, page
> > tables, stack, vmalloc, etc) on multiple levels (global, per-node,
> > per-memcg, etc). These stats give insights to users to how much memory
> > is used by the kernel and for what purposes.
> >
> > Currently, memory used by kvm for its page tables is not accounted in
> > the pagetable stats. This patch series accounts the memory pages used by
> > KVM for page tables in those stats.
>
> It's still not obvious to me that piggybacking NR_PAGETABLE is desirable, probably
> because I am quite clueless as to how these stats are used on the backend.  E.g.
> why not have a NR_SECONDARY_PAGETABLE entry to track pages used for secondary MMU
> page tables?

We can add NR_SECONDARY_PAGETABLE or even NR_KVM_PAGETABLE, but I am
not sure whether this separation is desired on the MM side. Let's see
what MM folks think about this.