diff options
author | Nir Weiner <nir.weiner@oracle.com> | 2019-01-27 12:17:16 +0200 |
---|---|---|
committer | Paolo Bonzini <pbonzini@redhat.com> | 2019-02-20 22:48:51 +0100 |
commit | dee339b5c1da3e6fa139b97f74f99dc9f0b03ff6 (patch) | |
tree | 6693b07487412d7ca10a17cf07d31dcdb9d43fe0 | |
parent | 49113d360bdeb4dd916fb6bffbcc3e157422b6fd (diff) |
KVM: Never start grow vCPU halt_poll_ns from value below halt_poll_ns_grow_start
grow_halt_poll_ns() have a strange behaviour in case
(vcpu->halt_poll_ns != 0) &&
(vcpu->halt_poll_ns < halt_poll_ns_grow_start).
In this case, vcpu->halt_poll_ns will be multiplied by grow factor
(halt_poll_ns_grow) which will require several grow iteration in order
to reach a value bigger than halt_poll_ns_grow_start.
This means that growing vcpu->halt_poll_ns from value of 0 is slower
than growing it from a positive value less than halt_poll_ns_grow_start.
Which is misleading and inaccurate.
Fix issue by changing grow_halt_poll_ns() to set vcpu->halt_poll_ns
to halt_poll_ns_grow_start in any case that
(vcpu->halt_poll_ns < halt_poll_ns_grow_start).
Regardless if vcpu->halt_poll_ns is 0.
use READ_ONCE to get a consistent number for all cases.
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Nir Weiner <nir.weiner@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r-- | arch/powerpc/kvm/book3s_hv.c | 5 | ||||
-rw-r--r-- | virt/kvm/kvm_main.c | 10 |
2 files changed, 7 insertions, 8 deletions
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 29ffc99bd79b..062f3c92c871 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -3634,10 +3634,9 @@ static void grow_halt_poll_ns(struct kvmppc_vcore *vc) if (!halt_poll_ns_grow) return; - if (vc->halt_poll_ns == 0) + vc->halt_poll_ns *= halt_poll_ns_grow; + if (vc->halt_poll_ns < halt_poll_ns_grow_start) vc->halt_poll_ns = halt_poll_ns_grow_start; - else - vc->halt_poll_ns *= halt_poll_ns_grow; } static void shrink_halt_poll_ns(struct kvmppc_vcore *vc) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index ae818d27a1a4..5087cf703ed1 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2189,17 +2189,17 @@ void kvm_sigset_deactivate(struct kvm_vcpu *vcpu) static void grow_halt_poll_ns(struct kvm_vcpu *vcpu) { - unsigned int old, val, grow; + unsigned int old, val, grow, grow_start; old = val = vcpu->halt_poll_ns; + grow_start = READ_ONCE(halt_poll_ns_grow_start); grow = READ_ONCE(halt_poll_ns_grow); if (!grow) goto out; - if (val == 0) - val = halt_poll_ns_grow_start; - else - val *= grow; + val *= grow; + if (val < grow_start) + val = grow_start; if (val > halt_poll_ns) val = halt_poll_ns; |