The kvm structure is pretty large. A large portion of it is the vcpu array, which is 4kB on x86_64 and arm64 as they deal with 512 vcpu VMs. Of course, hardly anyone runs VMs this big, so this is often a net waste of memory and cache locality.
A possible approach is to turn the fixed-size array into an xarray, which results in a net code deletion after a bit of cleanup. This series is on top of the current linux/master as it touches the RISC-V implementation. Only tested on arm64. Marc Zyngier (5): KVM: Move wiping of the kvm->vcpus array to common code KVM: mips: Use kvm_get_vcpu() instead of open-coded access KVM: s390: Use kvm_get_vcpu() instead of open-coded access KVM: x86: Use kvm_get_vcpu() instead of open-coded access KVM: Convert the kvm->vcpus array to a xarray arch/arm64/kvm/arm.c | 10 +--------- arch/mips/kvm/loongson_ipi.c | 4 ++-- arch/mips/kvm/mips.c | 23 ++--------------------- arch/powerpc/kvm/powerpc.c | 10 +--------- arch/riscv/kvm/vm.c | 10 +--------- arch/s390/kvm/kvm-s390.c | 26 ++++++-------------------- arch/x86/kvm/vmx/posted_intr.c | 2 +- arch/x86/kvm/x86.c | 9 +-------- include/linux/kvm_host.h | 7 ++++--- virt/kvm/kvm_main.c | 33 ++++++++++++++++++++++++++------- 10 files changed, 45 insertions(+), 89 deletions(-) -- 2.30.2
