On Sat, 30 Nov 2019 03:14:43 +0000, Heyi Guo <guoheyi@xxxxxxxxxx> wrote: > > Platforms running hypervisor nowadays are normally powerful servers > which at least support GICv3, so it should be better to switch > kvm_vgic_global_state.gicv3_cpuif to static likely branch, which can > reduce two "b" instructions to a single "nop" for GICv3 branches. > > We don't update arm32 specific code for they may still only have > GICv2. There is a number of disputable statements here. Out of the fairly large zoo of arm64 systems I have access to, 75% of them are based on GICv2, so they are still the overwhelming majority. Yes, they all run KVM (otherwise I would ignore them). Furthermore, I would expect that "powerful servers" are perfectly capable to execute a couple of branches without breaking a sweat. Finally, you don't provide any number supporting that: - GICv3 systems see a performance improvement across the large variety of CPU implementations - GICv2 systems don't see a performance regression Once you provide such numbers, I'll reevaluate my position. Until then, I'm not considering this kind of change. Thanks, M. -- Jazz is not dead, it just smells funny. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
