On Tue, 22 Dec 2020 09:07:39 -0800 Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > On Mon, Dec 21, 2020, Zdenek Kaspar wrote: > > [ 179.364305] WARNING: CPU: 0 PID: 369 at > > kvm_mmu_zap_oldest_mmu_pages+0xd1/0xe0 [kvm] [ 179.365415] Call > > Trace: [ 179.365443] paging64_page_fault+0x244/0x8e0 [kvm] > > This means the shadow page zapping is occuring because KVM is hitting > the max number of allowed MMU shadow pages. Can you provide your > QEMU command line? I can reproduce the performance degredation, but > only by deliberately overriding the max number of MMU pages via > `-machine kvm-shadow-mem` to be an absurdly low value. > > > [ 179.365596] kvm_mmu_page_fault+0x376/0x550 [kvm] > > [ 179.365725] kvm_arch_vcpu_ioctl_run+0xbaf/0x18f0 [kvm] > > [ 179.365772] kvm_vcpu_ioctl+0x203/0x520 [kvm] > > [ 179.365938] __x64_sys_ioctl+0x338/0x720 > > [ 179.365992] do_syscall_64+0x33/0x40 > > [ 179.366013] entry_SYSCALL_64_after_hwframe+0x44/0xa9 It's one long line, added "\" for mail readability: qemu-system-x86_64 -machine type=q35,accel=kvm \ -cpu host,host-cache-info=on -smp cpus=2,cores=2 \ -m size=1024 -global virtio-pci.disable-legacy=on \ -global virtio-pci.disable-modern=off \ -device virtio-balloon \ -device virtio-net,netdev=tap-build,mac=DE:AD:BE:EF:00:80 \ -object rng-random,filename=/dev/urandom,id=rng0 \ -device virtio-rng,rng=rng0 \ -name build,process=qemu-build \ -drive file=/mnt/data/export/unix/kvm/build/openbsd-amd64.img,if=virtio,cache=none,format=raw,aio=native \ -netdev type=tap,id=tap-build,vhost=on \ -serial none \ -parallel none \ -monitor unix:/dev/shm/kvm-build.sock,server,nowait \ -enable-kvm -daemonize -runas qemu Z.
