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? > > 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 > > Stefan
