To share my test result, I do NOT reproduce the issue with the below command line and QEMU-8.2.
However, I can reproduce with QEMU-6.2. The mainloop consumes 100% CPU usage. qemu-system-x86_64 \ --enable-kvm -cpu host -smp 2 -m 8G \ -object throttle-group,id=limit0,x-iops-total=200,x-iops-total-max=200,x-bps-total-max-length=1,x-bps-read-max-length=1,x-bps-write-max-length=1,x-iops-total-max-length=1,x-iops-read-max-length=1,x-iops-write-max-length=1 \ -object throttle-group,id=limit1,x-iops-total=250,x-iops-total-max=250,x-bps-total-max-length=1,x-bps-read-max-length=1,x-bps-write-max-length=1,x-iops-total-max-length=1,x-iops-read-max-length=1,x-iops-write-max-length=1 \ -object throttle-group,id=limit2,x-iops-total=300,x-iops-total-max=300,x-bps-total-max-length=1,x-bps-read-max-length=1,x-bps-write-max-length=1,x-iops-total-max-length=1,x-iops-read-max-length=1,x-iops-write-max-length=1 \ -object throttle-group,id=limit012,x-iops-total=400,x-iops-total-max=400,x-bps-total-max-length=1,x-bps-read-max-length=1,x-bps-write-max-length=1,x-iops-total-max-length=1,x-iops-read-max-length=1,x-iops-write-max-length=1 \ -device virtio-blk-pci,bus=pci.0,addr=0x4,drive=libvirt-4-format,id=virtio-disk0,bootindex=1 \ -blockdev driver=file,filename=image.qcow2,node-name=libvirt-4-storage,discard=unmap \ -blockdev node-name=libvirt-4-format,driver=qcow2,file=libvirt-4-storage \ -device virtio-blk-pci,bus=pci.0,addr=0x5,drive=libvirt-6-filter,id=virtio-disk1 \ -blockdev driver=file,filename=test01.qcow2,node-name=libvirt-3-storage,discard=unmap \ -blockdev node-name=libvirt-3-format,driver=qcow2,file=libvirt-3-storage \ -blockdev driver=throttle,node-name=libvirt-5-filter,throttle-group=limit0,file=libvirt-3-format \ -blockdev driver=throttle,node-name=libvirt-6-filter,throttle-group=limit012,file=libvirt-5-filter \ -device virtio-blk-pci,bus=pci.0,addr=0x6,drive=libvirt-4-filter,id=virtio-disk2 \ -blockdev driver=file,filename=test02.qcow2,node-name=libvirt-2-storage,discard=unmap \ -blockdev node-name=libvirt-2-format,driver=qcow2,file=libvirt-2-storage \ -blockdev driver=throttle,node-name=libvirt-3-filter,throttle-group=limit1,file=libvirt-2-format \ -blockdev driver=throttle,node-name=libvirt-4-filter,throttle-group=limit012,file=libvirt-3-filter \ -device virtio-blk-pci,bus=pci.0,addr=0x7,drive=libvirt-2-filter,id=virtio-disk3 \ -blockdev driver=file,filename=test03.qcow2,node-name=libvirt-1-storage,discard=unmap \ -blockdev node-name=libvirt-1-format,driver=qcow2,file=libvirt-1-storage \ -blockdev driver=throttle,node-name=libvirt-1-filter,throttle-group=limit2,file=libvirt-1-format \ -blockdev driver=throttle,node-name=libvirt-2-filter,throttle-group=limit012,file=libvirt-1-filter \ -netdev user,id=user0,hostfwd=tcp::5028-:22 \ -device virtio-net-pci,netdev=user0,id=net0,mac=52:54:00:12:34:56,bus=pci.0,addr=0x3 \ -monitor stdio (qemu) info status (qemu) savevm snapshot1 (qemu) loadvm snapshot1 Dongli Zhang On 3/28/24 03:50, Chun Feng Wu wrote: > BTW, if I download > qemu8.0(https://urldefense.com/v3/__https://download.qemu.org/qemu-8.0.0.tar.xz__;!!ACWV5N9M2RV99hQ!ObhT3ZYGr8GQFt4p7dWc-t-CFeKff1UzyRPc9WQrAuhz1B7jDC1-VTqjoCUDcrhXsffyBQuRtnoZhfZhS8FVig$ > ), compile and install it in my ubuntu22.04, launch vm with the same > command(just update --machine to be "pc"), the host cpu usage is not high, it > seems to be a bug in QEMU6 > > Also, I have another question, for disk iotune or throttle group, after > reverting snapshot, if I login vm, and run fio, I/O performance drops a lot in > both QEMU6 and QEMU8, do anyone know the reason? Any explanation would be > appreciated! > > > > On 2024/3/28 07:32, Chun Feng Wu wrote: >> >> Hi, >> >> I am testing throttle filter chain(multiple throttle-groups on disk) with the >> following steps: >> 1. start guest vm(chained throttle filters applied on disk per >> https://urldefense.com/v3/__https://github.com/qemu/qemu/blob/master/docs/throttle.txt__;!!ACWV5N9M2RV99hQ!ObhT3ZYGr8GQFt4p7dWc-t-CFeKff1UzyRPc9WQrAuhz1B7jDC1-VTqjoCUDcrhXsffyBQuRtnoZhfaQOXc8pg$ >> ) >> 2. take snapshot >> 3. revert snapshot >> >> after step3, I noticed qemu process in host consumes 100% cpu, and after I >> login guest vm, vm cannot(or slowly) response my cmd (it works well before >> reverting). >> >> / PID USER PR NI VIRT RES SHR S %CPU %MEM >> TIME+ COMMAND >> 65455 root 20 0 9659924 891328 20132 R 100.3 5.4 29:39.93 >> qemu-system-x86/ >> >> / >> / >> >> Does anybody know why such issue happens? is it a bug or I misunderstand >> something? >> >> my cmd: >> >> /qemu-system-x86_64 \ >> -name ubuntu-20.04-vm,debug-threads=on \ >> -machine pc-i440fx-jammy,usb=off,dump-guest-core=off \ >> -accel kvm \ >> -cpu >> Broadwell-IBRS,vme=on,ss=on,vmx=on,f16c=on,rdrand=on,hypervisor=on,arat=on,tsc-adjust=on,md-clear=on,stibp=on,ssbd=on,xsaveopt=on,pdpe1gb=on,abm=on,tsx-ctrl=off,hle=off,rtm=off >> \ >> -m 8192 \ >> -overcommit mem-lock=off \ >> -smp 2,sockets=1,dies=1,cores=1,threads=2 \ >> -numa node,nodeid=0,cpus=0-1,memdev=ram \ >> -object memory-backend-ram,id=ram,size=8192M \ >> -uuid d2d68f5d-bff0-4167-bbc3-643e3566b8fb \ >> -display none \ >> -nodefaults \ >> -monitor stdio \ >> -rtc base=utc,driftfix=slew \ >> -no-shutdown \ >> -boot strict=on \ >> -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 \ >> -object >> '{"qom-type":"throttle-group","id":"limit0","limits":{"bps-total":0,"bps-read":0,"bps-write":0,"iops-total":200,"iops-read":0,"iops-write":0,"bps-total-max":0,"bps-read-max":0,"bps-write-max":0,"iops-total-max":200,"iops-read-max":0,"iops-write-max":0,"iops-size":0,"bps-total-max-length":1,"bps-read-max-length":1,"bps-write-max-length":1,"iops-total-max-length":1,"iops-read-max-length":1,"iops-write-max-length":1}}' >> \ >> -object >> '{"qom-type":"throttle-group","id":"limit1","limits":{"bps-total":0,"bps-read":0,"bps-write":0,"iops-total":250,"iops-read":0,"iops-write":0,"bps-total-max":0,"bps-read-max":0,"bps-write-max":0,"iops-total-max":250,"iops-read-max":0,"iops-write-max":0,"iops-size":0,"bps-total-max-length":1,"bps-read-max-length":1,"bps-write-max-length":1,"iops-total-max-length":1,"iops-read-max-length":1,"iops-write-max-length":1}}' >> \ >> -object >> '{"qom-type":"throttle-group","id":"limit2","limits":{"bps-total":0,"bps-read":0,"bps-write":0,"iops-total":300,"iops-read":0,"iops-write":0,"bps-total-max":0,"bps-read-max":0,"bps-write-max":0,"iops-total-max":300,"iops-read-max":0,"iops-write-max":0,"iops-size":0,"bps-total-max-length":1,"bps-read-max-length":1,"bps-write-max-length":1,"iops-total-max-length":1,"iops-read-max-length":1,"iops-write-max-length":1}}' >> \ >> -object >> '{"qom-type":"throttle-group","id":"limit012","limits":{"bps-total":0,"bps-read":0,"bps-write":0,"iops-total":400,"iops-read":0,"iops-write":0,"bps-total-max":0,"bps-read-max":0,"bps-write-max":0,"iops-total-max":400,"iops-read-max":0,"iops-write-max":0,"iops-size":0,"bps-total-max-length":1,"bps-read-max-length":1,"bps-write-max-length":1,"iops-total-max-length":1,"iops-read-max-length":1,"iops-write-max-length":1}}' >> \ >> -blockdev >> '{"driver":"file","filename":"/virt/images/focal-server-cloudimg-amd64.img","node-name":"libvirt-4-storage","auto-read-only":true,"discard":"unmap"}' >> \ >> -blockdev >> '{"node-name":"libvirt-4-format","read-only":false,"driver":"qcow2","file":"libvirt-4-storage","backing":null}' >> \ >> -device >> virtio-blk-pci,bus=pci.0,addr=0x4,drive=libvirt-4-format,id=virtio-disk0,bootindex=1 >> \ >> -blockdev >> '{"driver":"file","filename":"/virt/disks/vm1_disk_1.qcow2","node-name":"libvirt-3-storage","auto-read-only":true,"discard":"unmap"}' >> \ >> -blockdev >> '{"node-name":"libvirt-3-format","read-only":false,"driver":"qcow2","file":"libvirt-3-storage","backing":null}' >> \ >> -blockdev >> '{"driver":"throttle","node-name":"libvirt-5-filter","throttle-group":"limit0","file":"libvirt-3-format"}' >> \ >> -blockdev >> '{"driver":"throttle","node-name":"libvirt-6-filter","throttle-group":"limit012","file":"libvirt-5-filter"}' >> \ >> -device >> virtio-blk-pci,bus=pci.0,addr=0x5,drive=libvirt-6-filter,id=virtio-disk1 \ >> -blockdev >> '{"driver":"file","filename":"/virt/disks/vm1_disk_2.qcow2","node-name":"libvirt-2-storage","auto-read-only":true,"discard":"unmap"}' >> \ >> -blockdev >> '{"node-name":"libvirt-2-format","read-only":false,"driver":"qcow2","file":"libvirt-2-storage","backing":null}' >> \ >> -blockdev >> '{"driver":"throttle","node-name":"libvirt-3-filter","throttle-group":"limit1","file":"libvirt-2-format"}' >> \ >> -blockdev >> '{"driver":"throttle","node-name":"libvirt-4-filter","throttle-group":"limit012","file":"libvirt-3-filter"}' >> \ >> -device >> virtio-blk-pci,bus=pci.0,addr=0x6,drive=libvirt-4-filter,id=virtio-disk2 \ >> -blockdev >> '{"driver":"file","filename":"/virt/disks/vm1_disk_3.qcow2","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' >> \ >> -blockdev >> '{"node-name":"libvirt-1-format","read-only":false,"driver":"qcow2","file":"libvirt-1-storage","backing":null}' >> \ >> -blockdev >> '{"driver":"throttle","node-name":"libvirt-1-filter","throttle-group":"limit2","file":"libvirt-1-format"}' >> \ >> -blockdev >> '{"driver":"throttle","node-name":"libvirt-2-filter","throttle-group":"limit012","file":"libvirt-1-filter"}' >> \ >> -device >> virtio-blk-pci,bus=pci.0,addr=0x7,drive=libvirt-2-filter,id=virtio-disk3 \ >> -netdev user,id=user0,hostfwd=tcp::2222-:22 \ >> -device >> virtio-net-pci,netdev=user0,id=net0,mac=52:54:00:12:34:56,bus=pci.0,addr=0x3 >> \ >> -chardev pty,id=charserial0 \ >> -device isa-serial,chardev=charserial0,id=serial0,index=0 \ >> -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x2 \ >> -sandbox >> on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \ >> -msg timestamp=on/ >> >> >> snapshot and reverting: >> >> /(qemu) info status >> VM status: running >> (qemu) savevm snapshot1 >> (qemu) loadvm snapshot1/ >> >> >> my env: >> /:~# qemu-system-x86_64 --version >> QEMU emulator version 6.2.0 (Debian 1:6.2+dfsg-2ubuntu6.17) >> Copyright (c) 2003-2021 Fabrice Bellard and the QEMU Project developers >> >> :~# lsb_release -a >> No LSB modules are available. >> Distributor ID: Ubuntu >> Description: Ubuntu 22.04.4 LTS >> Release: 22.04 >> Codename: jammy/ >> >> -- >> Thanks and Regards, >> >> Wu >
