From: Mihai Caraman <mihai.caraman@freescale.com>
To: <kvm-ppc@vger.kernel.org>
Cc: Scott Wood <scottwood@freescale.com>,
Mihai Caraman <mihai.caraman@freescale.com>,
linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org
Subject: [PATCH v2] KVM: PPC: e500mc: Enhance tlb invalidation condition on vcpu schedule
Date: Tue, 17 Jun 2014 12:02:19 +0300 [thread overview]
Message-ID: <1402995739-23756-1-git-send-email-mihai.caraman@freescale.com> (raw)
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 taking into account the 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@freescale.com>
Cc: Scott Wood <scottwood@freescale.com>
---
v2:
- improve patch name and description
- add performance results
arch/powerpc/kvm/e500mc.c | 20 +++++++++++++++++---
1 file changed, 17 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/kvm/e500mc.c b/arch/powerpc/kvm/e500mc.c
index 17e4562..d3b814b0 100644
--- a/arch/powerpc/kvm/e500mc.c
+++ b/arch/powerpc/kvm/e500mc.c
@@ -111,10 +111,12 @@ 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(int, last_lpid_on_cpu);
static void kvmppc_core_vcpu_load_e500mc(struct kvm_vcpu *vcpu, int cpu)
{
struct kvmppc_vcpu_e500 *vcpu_e500 = to_e500(vcpu);
+ bool update_last = false, inval_tlb = false;
kvmppc_booke_vcpu_load(vcpu, cpu);
@@ -140,12 +142,24 @@ static void kvmppc_core_vcpu_load_e500mc(struct kvm_vcpu *vcpu, int cpu)
mtspr(SPRN_GDEAR, vcpu->arch.shared->dar);
mtspr(SPRN_GESR, vcpu->arch.shared->esr);
- if (vcpu->arch.oldpir != mfspr(SPRN_PIR) ||
- __get_cpu_var(last_vcpu_on_cpu) != vcpu) {
- kvmppc_e500_tlbil_all(vcpu_e500);
+ if (vcpu->arch.oldpir != mfspr(SPRN_PIR)) {
+ /* stale tlb entries */
+ inval_tlb = update_last = true;
+ } else if (__get_cpu_var(last_vcpu_on_cpu) != vcpu) {
+ update_last = true;
+ /* polluted tlb entries */
+ inval_tlb = __get_cpu_var(last_lpid_on_cpu) ==
+ vcpu->kvm->arch.lpid;
+ }
+
+ if (update_last) {
__get_cpu_var(last_vcpu_on_cpu) = vcpu;
+ __get_cpu_var(last_lpid_on_cpu) = vcpu->kvm->arch.lpid;
}
+ if (inval_tlb)
+ kvmppc_e500_tlbil_all(vcpu_e500);
+
kvmppc_load_guest_fp(vcpu);
}
--
1.7.11.7
next reply other threads:[~2014-06-17 9:02 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-17 9:02 Mihai Caraman [this message]
2014-06-17 15:35 ` [PATCH v2] KVM: PPC: e500mc: Enhance tlb invalidation condition on vcpu schedule Scott Wood
2014-06-17 19:04 ` mihai.caraman
2014-06-17 19:05 ` Scott Wood
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