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Re: QEMU 5.0 virtio-blk performance regression with high queue depths
From: |
Stefan Hajnoczi |
Subject: |
Re: QEMU 5.0 virtio-blk performance regression with high queue depths |
Date: |
Wed, 16 Sep 2020 14:32:58 +0100 |
On Thu, Aug 27, 2020 at 3:24 PM Stefan Hajnoczi <stefanha@gmail.com> 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
- Re: QEMU 5.0 virtio-blk performance regression with high queue depths,
Stefan Hajnoczi <=