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authorNir Weiner <nir.weiner@oracle.com>2019-01-27 12:17:16 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2019-02-20 22:48:51 +0100
commitdee339b5c1da3e6fa139b97f74f99dc9f0b03ff6 (patch)
tree6693b07487412d7ca10a17cf07d31dcdb9d43fe0 /arch/powerpc/kvm
parent49113d360bdeb4dd916fb6bffbcc3e157422b6fd (diff)
downloadlinux-dee339b5c1da3e6fa139b97f74f99dc9f0b03ff6.tar.bz2
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>
Diffstat (limited to 'arch/powerpc/kvm')
-rw-r--r--arch/powerpc/kvm/book3s_hv.c5
1 files changed, 2 insertions, 3 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)