On 9/16/20 4:32 PM, Stefan Hajnoczi wrote: > On Thu, Aug 27, 2020 at 3:24 PM Stefan Hajnoczi <[email protected]> wrote: >> Hi Denis, >> A performance regression was found after the virtio-blk queue-size >> property was increased from 128 to 256 in QEMU 5.0 in commit >> c9b7d9ec21dfca716f0bb3b68dee75660d86629c ("virtio: increase virtqueue >> size for virtio-scsi and virtio-blk"). I wanted to let you know if case >> you have ideas or see something similar. > Ping, have you noticed performance regressions after switching to > virtio-blk queue-size 256? oops, I have missed original letter.
Denis Plotnikov have left the team at the moment. >> Throughput and IOPS of the following fio benchmarks dropped by 30-40%: >> >> # mkfs.xfs /dev/vdb >> # mount /dev/vdb /mnt >> # fio --rw=%s --bs=%s --iodepth=64 --runtime=1m --direct=1 >> --filename=/mnt/%s --name=job1 --ioengine=libaio --thread --group_reporting >> --numjobs=16 --size=512MB --time_based --output=/tmp/fio_result &> /dev/null >> - rw: read write >> - bs: 4k 64k >> >> Note that there are 16 threads submitting 64 requests each! The guest >> block device queue depth will be maxed out. The virtqueue should be full >> most of the time. >> >> Have you seen regressions after virtio-blk queue-size was increased in >> QEMU 5.0? >> >> Here are the details of the host storage: >> >> # mkfs.xfs /dev/sdb # 60GB SSD drive >> # mount /dev/sdb /mnt/test >> # qemu-img create -f qcow2 /mnt/test/storage2.qcow2 40G >> >> The guest command-line is: >> >> # MALLOC_PERTURB_=1 numactl \ >> -m 1 /usr/libexec/qemu-kvm \ >> -S \ >> -name 'avocado-vt-vm1' \ >> -sandbox on \ >> -machine q35 \ >> -device >> pcie-root-port,id=pcie-root-port-0,multifunction=on,bus=pcie.0,addr=0x1,chassis=1 >> \ >> -device >> pcie-pci-bridge,id=pcie-pci-bridge-0,addr=0x0,bus=pcie-root-port-0 \ >> -nodefaults \ >> -device VGA,bus=pcie.0,addr=0x2 \ >> -m 4096 \ >> -smp 2,maxcpus=2,cores=1,threads=1,dies=1,sockets=2 \ >> -cpu 'IvyBridge',+kvm_pv_unhalt \ >> -chardev >> socket,server,id=qmp_id_qmpmonitor1,nowait,path=/var/tmp/avocado_bapfdqao/monitor-qmpmonitor1-20200721-014154-5HJGMjxW >> \ >> -mon chardev=qmp_id_qmpmonitor1,mode=control \ >> -chardev >> socket,server,id=qmp_id_catch_monitor,nowait,path=/var/tmp/avocado_bapfdqao/monitor-catch_monitor-20200721-014154-5HJGMjxW >> \ >> -mon chardev=qmp_id_catch_monitor,mode=control \ >> -device pvpanic,ioport=0x505,id=id31BN83 \ >> -chardev >> socket,server,id=chardev_serial0,nowait,path=/var/tmp/avocado_bapfdqao/serial-serial0-20200721-014154-5HJGMjxW >> \ >> -device isa-serial,id=serial0,chardev=chardev_serial0 \ >> -chardev >> socket,id=seabioslog_id_20200721-014154-5HJGMjxW,path=/var/tmp/avocado_bapfdqao/seabios-20200721-014154-5HJGMjxW,server,nowait >> \ >> -device >> isa-debugcon,chardev=seabioslog_id_20200721-014154-5HJGMjxW,iobase=0x402 \ >> -device >> pcie-root-port,id=pcie-root-port-1,port=0x1,addr=0x1.0x1,bus=pcie.0,chassis=2 >> \ >> -device qemu-xhci,id=usb1,bus=pcie-root-port-1,addr=0x0 \ >> -device usb-tablet,id=usb-tablet1,bus=usb1.0,port=1 \ >> -blockdev >> node-name=file_image1,driver=file,aio=threads,filename=rootfs.qcow2,cache.direct=on,cache.no-flush=off >> \ >> -blockdev >> node-name=drive_image1,driver=qcow2,cache.direct=on,cache.no-flush=off,file=file_image1 >> \ >> -device >> pcie-root-port,id=pcie-root-port-2,port=0x2,addr=0x1.0x2,bus=pcie.0,chassis=3 >> \ >> -device >> virtio-blk-pci,id=image1,drive=drive_image1,bootindex=0,write-cache=on,bus=pcie-root-port-2,addr=0x0 >> \ >> -blockdev >> node-name=file_disk1,driver=file,aio=threads,filename=/mnt/test/storage2.qcow2,cache.direct=on,cache.no-flush=off >> \ >> -blockdev >> node-name=drive_disk1,driver=qcow2,cache.direct=on,cache.no-flush=off,file=file_disk1 >> \ >> -device >> pcie-root-port,id=pcie-root-port-3,port=0x3,addr=0x1.0x3,bus=pcie.0,chassis=4 >> \ >> -device >> virtio-blk-pci,id=disk1,drive=drive_disk1,bootindex=1,write-cache=on,bus=pcie-root-port-3,addr=0x0 >> \ >> -device >> pcie-root-port,id=pcie-root-port-4,port=0x4,addr=0x1.0x4,bus=pcie.0,chassis=5 >> \ >> -device >> virtio-net-pci,mac=9a:37:37:37:37:4e,id=idBMd7vy,netdev=idLb51aS,bus=pcie-root-port-4,addr=0x0 >> \ >> -netdev tap,id=idLb51aS,fd=14 \ >> -vnc :0 \ >> -rtc base=utc,clock=host,driftfix=slew \ >> -boot menu=off,order=cdn,once=c,strict=off \ >> -enable-kvm \ >> -device >> pcie-root-port,id=pcie_extra_root_port_0,multifunction=on,bus=pcie.0,addr=0x3,chassis=6 I will make a check today. Talking about our performance measurements, we have not seen ANY performance degradation, especially 30-40%. This looking quite strange to me. Though there is quite important difference. We are always using O_DIRECT and 'native' AIO engine. Den
