[PATCH v2 16/43] KVM: Don't redo ktime_get() when calculating halt-polling stop/deadline
Sean Christopherson <[email protected]>
| Newsgroups | org.kernel.vger.kvm-ppc,dev.linux.lists.kvmarm,org.infradead.lists.kvm-riscv,org.infradead.lists.linux-arm-kernel,org.infradead.lists.linux-riscv,org.kernel.vger.kvm,org.kernel.vger.linux-kernel,org.kernel.vger.linux-mips |
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| Message-ID | <[email protected]> |
Calculate the halt-polling "stop" time using "cur" instead of redoing ktime_get(). In the happy case where hardware correctly predicts do_halt_poll, "cur" is only a few cycles old. And if the branch is mispredicted, arguably that extra latency should count toward the halt-polling time. In all likelihood, the numbers involved are in the noise and either approach is perfectly ok. Reviewed-by: David Matlack <[email protected]> Signed-off-by: Sean Christopherson <[email protected]> --- virt/kvm/kvm_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index a36ccdc93a72..481e8178b43d 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3272,7 +3272,7 @@ void kvm_vcpu_halt(struct kvm_vcpu *vcpu) start = cur = poll_end = ktime_get(); if (do_halt_poll) { - ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns); + ktime_t stop = ktime_add_ns(cur, vcpu->halt_poll_ns); do { /* -- 2.33.0.882.g93a45727a2-goog