On Wed, 2014-06-18 at 10:15 +0300, Mihai Caraman wrote:
> On vcpu schedule, the condition checked for tlb pollution is too loose.
> The tlb entries of a vcpu become polluted (vs stale) only when a different
> vcpu within the same logical partition runs in-between. Optimize the tlb
> invalidation condition keeping last_vcpu per logical partition id.
>
> With the new invalidation condition, a guest shows 4% performance improvement
> on P5020DS while running a memory stress application with the cpu
> oversubscribed,
> the other guest running a cpu intensive workload.
>
> Guest - old invalidation condition
> real 3.89
> user 3.87
> sys 0.01
>
> Guest - enhanced invalidation condition
> real 3.75
> user 3.73
> sys 0.01
>
> Host
> real 3.70
> user 1.85
> sys 0.00
>
> The memory stress application accesses 4KB pages backed by 75% of available
> TLB0 entries:
>
> char foo[ENTRIES][4096] __attribute__ ((aligned (4096)));
>
> int main()
> {
> char bar;
> int i, j;
>
> for (i = 0; i < ITERATIONS; i++)
> for (j = 0; j < ENTRIES; j++)
> bar = foo[j][0];
>
> return 0;
> }
>
> Signed-off-by: Mihai Caraman <mihai.cara...@freescale.com>
> Cc: Scott Wood <scottw...@freescale.com>
> ---
> v4:
> - rename last_vcpu_on_cpu to last_vcpu_of_lpid
> - use "*[" syntax despite checkpatch error
>
> v3:
> - use existing logic while keeping last_cpu per lpid
>
> arch/powerpc/kvm/e500mc.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/kvm/e500mc.c b/arch/powerpc/kvm/e500mc.c
> index 17e4562..690499d 100644
> --- a/arch/powerpc/kvm/e500mc.c
> +++ b/arch/powerpc/kvm/e500mc.c
> @@ -110,7 +110,7 @@ void kvmppc_mmu_msr_notify(struct kvm_vcpu *vcpu, u32
> old_msr)
> {
> }
>
> -static DEFINE_PER_CPU(struct kvm_vcpu *, last_vcpu_on_cpu);
> +static DEFINE_PER_CPU(struct kvm_vcpu *[KVMPPC_NR_LPIDS], last_vcpu_of_lpid);
>
> static void kvmppc_core_vcpu_load_e500mc(struct kvm_vcpu *vcpu, int cpu)
> {
> @@ -141,9 +141,9 @@ static void kvmppc_core_vcpu_load_e500mc(struct kvm_vcpu
> *vcpu, int cpu)
> mtspr(SPRN_GESR, vcpu->arch.shared->esr);
>
> if (vcpu->arch.oldpir != mfspr(SPRN_PIR) ||
> - __get_cpu_var(last_vcpu_on_cpu) != vcpu) {
> + __get_cpu_var(last_vcpu_of_lpid)[vcpu->kvm->arch.lpid] != vcpu) {
> kvmppc_e500_tlbil_all(vcpu_e500);
> - __get_cpu_var(last_vcpu_on_cpu) = vcpu;
> + __get_cpu_var(last_vcpu_of_lpid)[vcpu->kvm->arch.lpid] = vcpu;
> }
>
> kvmppc_load_guest_fp(vcpu);
Reviewed-by: Scott Wood <scottw...@freescale.com>
-Scott
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