On Fri, May 13, 2022 at 9:12 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > [...] > > It was mostly an honest question, I too am trying to understand what userspace > wants to do with this information. I was/am also trying to understand the benefits > of doing the tracking through page_state and not a dedicated KVM stat. E.g. KVM > already has specific stats for the number of leaf pages mapped into a VM, why not > do the same for non-leaf pages? Let me answer why a more general stat is useful and the potential userspace reaction: For a memory type which is significant enough, it is useful to expose it in the general interfaces, so that the general data/stat collection infra can collect them instead of having workload dependent stat collectors. In addition, not necessarily that stat has to have a userspace reaction in an online fashion. We do collect stats for offline analysis which greatly influence the priority order of optimization workitems. Next the question is do we really need a separate stat item (secondary_pagetable instead of just plain pagetable) exposed in the stable API? To me secondary_pagetable is general (not kvm specific) enough and can be significant, so having a separate dedicated stat should be ok. Though I am ok with lump it with pagetable stat for now but we do want it to be accounted somewhere.
