From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sean Christopherson Date: Sat, 25 Sep 2021 00:55:17 +0000 Subject: [PATCH 03/14] KVM: Refactor and document halt-polling stats update helper Message-Id: <20210925005528.1145584-4-seanjc@google.com> List-Id: References: <20210925005528.1145584-1-seanjc@google.com> In-Reply-To: <20210925005528.1145584-1-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Christian Borntraeger , Janosch Frank , Paolo Bonzini Cc: James Morse , Alexandru Elisei , Suzuki K Poulose , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, linux-kernel@vger.kernel.org, David Matlack , Jing Zhang Add a comment to document that halt-polling is considered successful even if the polling loop itself didn't detect a wake event, i.e. if a wake event was detect in the final kvm_vcpu_check_block(). Invert the param to the update helper so that the helper is a dumb function that is "told" whether or not polling was successful, as opposed to having it determinine success/failure based on blocking behavior. Opportunistically tweak the params to the update helper to reduce the line length for the call site so that it fits on a single line, and so that the prototype conforms to the more traditional kernel style. No functional change intended. Signed-off-by: Sean Christopherson --- virt/kvm/kvm_main.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 8b33f5045b4d..12fe91a0a4c8 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3199,13 +3199,15 @@ static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu) return ret; } -static inline void -update_halt_poll_stats(struct kvm_vcpu *vcpu, u64 poll_ns, bool waited) +static inline void update_halt_poll_stats(struct kvm_vcpu *vcpu, ktime_t start, + ktime_t end, bool success) { - if (waited) - vcpu->stat.generic.halt_poll_fail_ns += poll_ns; - else + u64 poll_ns = ktime_to_ns(ktime_sub(end, start)); + + if (success) vcpu->stat.generic.halt_poll_success_ns += poll_ns; + else + vcpu->stat.generic.halt_poll_fail_ns += poll_ns; } /* @@ -3274,9 +3276,13 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) kvm_arch_vcpu_unblocking(vcpu); block_ns = ktime_to_ns(cur) - ktime_to_ns(start); + /* + * Note, halt-polling is considered successful so long as the vCPU was + * never actually scheduled out, i.e. even if the wake event arrived + * after of the halt-polling loop itself, but before the full wait. + */ if (do_halt_poll) - update_halt_poll_stats( - vcpu, ktime_to_ns(ktime_sub(poll_end, start)), waited); + update_halt_poll_stats(vcpu, start, poll_end, !waited); if (halt_poll_allowed) { if (!vcpu_valid_wakeup(vcpu)) { -- 2.33.0.685.g46640cef36-goog