summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorWanpeng Li <wanpengli@tencent.com>2018-02-13 09:05:41 +0800
committerRadim Krčmář <rkrcmar@redhat.com>2018-03-06 18:40:45 +0100
commitb2798ba0b8769b42f00899b44a538b5fcecb480d (patch)
treed62c2b5aadf73a3f60523e8cd65444c7605c3808
parenta4429e53c9b3082b05e51224c3d58dbdd39306c5 (diff)
KVM: X86: Choose qspinlock when dedicated physical CPUs are available
Waiman Long mentioned that: > Generally speaking, unfair lock performs well for VMs with a small > number of vCPUs. Native qspinlock may perform better than pvqspinlock > if there is vCPU pinning and there is no vCPU over-commitment. This patch uses the KVM_HINTS_DEDICATED performance hint, which is provided by the hypervisor admin, to choose the qspinlock algorithm when a dedicated physical CPU is available. PV_DEDICATED = 1, PV_UNHALT = anything: default is qspinlock PV_DEDICATED = 0, PV_UNHALT = 1: default is Hybrid PV queued/unfair lock PV_DEDICATED = 0, PV_UNHALT = 0: default is tas Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Eduardo Habkost <ehabkost@redhat.com> Signed-off-by: Wanpeng Li <wanpengli@tencent.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
-rw-r--r--arch/x86/kernel/kvm.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 8c9d98c46f84..f803e89e0b47 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -735,6 +735,11 @@ void __init kvm_spinlock_init(void)
if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
return;
+ if (kvm_para_has_hint(KVM_HINTS_DEDICATED)) {
+ static_branch_disable(&virt_spin_lock_key);
+ return;
+ }
+
__pv_init_lock_hash();
pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);