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authorWanpeng Li <wanpengli@tencent.com>2019-07-18 19:39:06 +0800
committerPaolo Bonzini <pbonzini@redhat.com>2019-07-20 09:00:45 +0200
commitd73eb57b80b98ae147e4e6a7d9877c2ba175f972 (patch)
treeccba1f1c06ddf700c7985bed379550541e31a80c
parentKVM: selftests: Remove superfluous define from vmx.c (diff)
downloadlinux-dev-d73eb57b80b98ae147e4e6a7d9877c2ba175f972.tar.xz
linux-dev-d73eb57b80b98ae147e4e6a7d9877c2ba175f972.zip
KVM: Boost vCPUs that are delivering interrupts
Inspired by commit 9cac38dd5d (KVM/s390: Set preempted flag during vcpu wakeup and interrupt delivery), we want to also boost not just lock holders but also vCPUs that are delivering interrupts. Most smp_call_function_many calls are synchronous, so the IPI target vCPUs are also good yield candidates. This patch introduces vcpu->ready to boost vCPUs during wakeup and interrupt delivery time; unlike s390 we do not reuse vcpu->preempted so that voluntarily preempted vCPUs are taken into account by kvm_vcpu_on_spin, but vmx_vcpu_pi_put is not affected (VT-d PI handles voluntary preemption separately, in pi_pre_block). Testing on 80 HT 2 socket Xeon Skylake server, with 80 vCPUs VM 80GB RAM: ebizzy -M vanilla boosting improved 1VM 21443 23520 9% 2VM 2800 8000 180% 3VM 1800 3100 72% Testing on my Haswell desktop 8 HT, with 8 vCPUs VM 8GB RAM, two VMs, one running ebizzy -M, the other running 'stress --cpu 2': w/ boosting + w/o pv sched yield(vanilla) vanilla boosting improved 1570 4000 155% w/ boosting + w/ pv sched yield(vanilla) vanilla boosting improved 1844 5157 179% w/o boosting, perf top in VM: 72.33% [kernel] [k] smp_call_function_many 4.22% [kernel] [k] call_function_i 3.71% [kernel] [k] async_page_fault w/ boosting, perf top in VM: 38.43% [kernel] [k] smp_call_function_many 6.31% [kernel] [k] async_page_fault 6.13% libc-2.23.so [.] __memcpy_avx_unaligned 4.88% [kernel] [k] call_function_interrupt Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Paul Mackerras <paulus@ozlabs.org> Cc: Marc Zyngier <maz@kernel.org> Signed-off-by: Wanpeng Li <wanpengli@tencent.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/s390/kvm/interrupt.c2
-rw-r--r--include/linux/kvm_host.h1
-rw-r--r--virt/kvm/kvm_main.c12
3 files changed, 10 insertions, 5 deletions
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 9dde4d7d8704..26f8bf4a22a7 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -1240,7 +1240,7 @@ void kvm_s390_vcpu_wakeup(struct kvm_vcpu *vcpu)
* The vcpu gave up the cpu voluntarily, mark it as a good
* yield-candidate.
*/
- vcpu->preempted = true;
+ vcpu->ready = true;
swake_up_one(&vcpu->wq);
vcpu->stat.halt_wakeup++;
}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index c5da875f19e3..5c5b5867024c 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -318,6 +318,7 @@ struct kvm_vcpu {
} spin_loop;
#endif
bool preempted;
+ bool ready;
struct kvm_vcpu_arch arch;
struct dentry *debugfs_dentry;
};
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b4ab59dd6846..887f3b0c2b60 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -314,6 +314,7 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
kvm_vcpu_set_in_spin_loop(vcpu, false);
kvm_vcpu_set_dy_eligible(vcpu, false);
vcpu->preempted = false;
+ vcpu->ready = false;
r = kvm_arch_vcpu_init(vcpu);
if (r < 0)
@@ -2387,6 +2388,7 @@ bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
wqp = kvm_arch_vcpu_wq(vcpu);
if (swq_has_sleeper(wqp)) {
swake_up_one(wqp);
+ WRITE_ONCE(vcpu->ready, true);
++vcpu->stat.halt_wakeup;
return true;
}
@@ -2500,7 +2502,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode)
continue;
} else if (pass && i > last_boosted_vcpu)
break;
- if (!READ_ONCE(vcpu->preempted))
+ if (!READ_ONCE(vcpu->ready))
continue;
if (vcpu == me)
continue;
@@ -4203,8 +4205,8 @@ static void kvm_sched_in(struct preempt_notifier *pn, int cpu)
{
struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn);
- if (vcpu->preempted)
- vcpu->preempted = false;
+ vcpu->preempted = false;
+ WRITE_ONCE(vcpu->ready, false);
kvm_arch_sched_in(vcpu, cpu);
@@ -4216,8 +4218,10 @@ static void kvm_sched_out(struct preempt_notifier *pn,
{
struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn);
- if (current->state == TASK_RUNNING)
+ if (current->state == TASK_RUNNING) {
vcpu->preempted = true;
+ WRITE_ONCE(vcpu->ready, true);
+ }
kvm_arch_vcpu_put(vcpu);
}