From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: [PATCH 0/5] KVM: x86: cleanup and minimal speedup for APICv Date: Fri, 14 Oct 2016 20:21:26 +0200 Message-ID: <1476469291-5039-1-git-send-email-pbonzini@redhat.com> Cc: rkrcmar@redhat.com, yang.zhang.wz@gmail.com, feng.wu@intel.com, mst@redhat.com To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On some benchmarks (e.g. netperf with ioeventfd disabled), APICv posted interrupts turn out to be slower than interrupt injection via KVM_REQ_EVENT. These patches save 40 cycles on kvm-unit-tests "inl" tests (1-2%), but I suspect the effect is bigger on workloads that inject interrupts heavily. Patches 1-2 are micro-optimization of the APICv vmentry code. The interesting one is patch 3. The aim is for APICv to not use KVM_REQ_EVENT at all for interrupts, therefore turning APICv's weakness (having to look at PIR on every vmentry) into a strength (because checking PIR.ON is cheaper than processing KVM_REQ_EVENT). I find that the new code overall makes more sense than the old one, and I like that more of the logic is contained within vmx_deliver_posted_interrupt and vmx_sync_pir_to_irr. KVM_REQ_EVENT did protect from mistakes, so the new code is more delicate, but I still prefer that to duct tape. :) Patches 4 and 5 are other cleanups. Paolo Paolo Bonzini (5): KVM: x86: avoid atomic operations on APICv vmentry KVM: x86: do not scan IRR twice on APICv vmentry KVM: x86: do not use KVM_REQ_EVENT for APICv interrupt injection KVM: x86: remove unnecessary sync_pir_to_irr KVM: vmx: clear pending interrupts on KVM_SET_LAPIC arch/x86/kvm/lapic.c | 45 +++++++++++++++++++++++++++++---------------- arch/x86/kvm/lapic.h | 4 ++-- arch/x86/kvm/vmx.c | 44 ++++++++++++++++++++++++++++++++------------ arch/x86/kvm/x86.c | 45 +++++++++++++++++++++++++-------------------- 4 files changed, 88 insertions(+), 50 deletions(-) -- 1.8.3.1