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| author | Nir Weiner <nir.weiner@oracle.com> | 2019-01-27 11:17:16 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2019-02-20 22:48:51 +0100 |
| commit | dee339b5c1da3e6fa139b97f74f99dc9f0b03ff6 (patch) | |
| tree | 6693b07487412d7ca10a17cf07d31dcdb9d43fe0 /arch/powerpc/kvm | |
| parent | KVM: Expose the initial start value in grow_halt_poll_ns() as a module parameter (diff) | |
| download | linux-dee339b5c1da3e6fa139b97f74f99dc9f0b03ff6.tar.xz linux-dee339b5c1da3e6fa139b97f74f99dc9f0b03ff6.zip | |
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.c | 5 |
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) |