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.caraman@xxxxxxxxxxxxx>
Cc: Scott Wood <scottwood@xxxxxxxxxxxxx>
---
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);
--
1.7.11.7
--
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