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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
