On Fri, Jul 12, 2024 at 8:06 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > On Wed, Jul 10, 2024, James Houghton wrote: > > 1. Drop the WAS_FAST complexity. > > 2. Add a function like mm_has_fast_aging_notifiers(), use that to > > determine if we should be doing look-around. > > I would prefer a flag over a function. Long-term, if my pseudo-lockless rmap > idea pans out, KVM can set the flag during VM creation. Until then, KVM can set > the flag during creation and then toggle it in (un)account_shadowed(). Races > will be possible, but they should be extremely rare and quite benign, all things > considered. So I think you're talking about .has_fast_aging bool on struct mmu_notifier, and we would do look-around if that is set, right? So we'd need to have something like mm_has_fast_aging_notifiers() to check if any of the subscribed mmu notifiers have .has_fast_aging. We could toggle it in (un)account_shadowed(), but I think I'd need to demonstrate some performance win to justify it.
