Re: [PATCH] KVM: MMU: increment stats after event occurrence

Davidlohr Bueso
2012-01-13T12:56:08Z

On Fri, 2012-01-13 at 10:24 +0900, Takuya Yoshikawa wrote:
> (2012/01/13 10:08), Davidlohr Bueso wrote:
> > From: Davidlohr Bueso<dave@gnu.org>
> >
> > It makes more sense to actually increment statistics for tlb flushes and page table entry updates after such _events_ occur, instead of before.
>
> Why?
>
>From a logical point of view its better to increase stats once the event
is processed - usually because it can fail and therefore the stats would
be incorrect.

> Takuya
>
> >
> > Signed-off-by: Davidlohr Bueso<dave@gnu.org>
> > ---
> > arch/x86/kvm/mmu.c | 4 ++--
> > 1 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> > index 2a2a9b4..0b7008e 100644
> > --- a/arch/x86/kvm/mmu.c
> > +++ b/arch/x86/kvm/mmu.c
> > @@ -3130,8 +3130,8 @@ static int nonpaging_init_context(struct kvm_vcpu *vcpu,
> >
> > void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu)
> > {
> > - ++vcpu->stat.tlb_flush;
> > kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
> > + ++vcpu->stat.tlb_flush;
> > }
> >
> > static void paging_new_cr3(struct kvm_vcpu *vcpu)
> > @@ -3486,8 +3486,8 @@ static void mmu_pte_write_new_pte(struct kvm_vcpu *vcpu,
> > return;
> > }
> >
> > - ++vcpu->kvm->stat.mmu_pte_updated;
> > vcpu->arch.mmu.update_pte(vcpu, sp, spte, new);
> > + ++vcpu->kvm->stat.mmu_pte_updated;
> > }
> >
> > static bool need_remote_flush(u64 old, u64 new)
>
>