Issue

What were you trying to do that didn't work? Using multiple iothreads (iothread-vq-mapping) on disk, the IO performance is worse than without iothread. and more iothreads not get better performance. Please provide the package NVR for which bug is seen: Red Hat Enterprise Linux release 9.4 Beta (Plow) 5.14.0-416.el9.x86_64 qemu-kvm-8.2.0-6.el9.x86_64 seabios-bin-1.16.3-2.el9.noarch edk2-ovmf-20231122-5.el9.noarch How reproducible: 100% Steps to reproduce 1.Boot VM with 4 data disk present disks with 0 iothread,1 iothread,2 iothreads and 4 iothreads /usr/libexec/qemu-kvm \ -S  \ -name 'avocado-vt-vm1'  \ -sandbox on \ -machine pc,memory-backend=mem-machine_mem  \ -nodefaults \ -device '\{"driver": "VGA", "bus": "pci.0", "addr": "0x2"}' \ -m 8192 \ -object '\{"size": 8589934592, "id": "mem-machine_mem", "qom-type": "memory-backend-ram"}'  \ -smp 16,maxcpus=16,cores=8,threads=1,dies=1,sockets=2  \ -cpu 'Icelake-Server-noTSX',+kvm_pv_unhalt \ \ -device '\{"driver": "ich9-usb-ehci1", "id": "usb1", "addr": "0x1d.0x7", "multifunction": true, "bus": "pci.0"}' \ -device '\{"driver": "ich9-usb-uhci1", "id": "usb1.0", "multifunction": true, "masterbus": "usb1.0", "addr": "0x1d.0x0", "firstport": 0, "bus": "pci.0"}' \ -device '\{"driver": "ich9-usb-uhci2", "id": "usb1.1", "multifunction": true, "masterbus": "usb1.0", "addr": "0x1d.0x2", "firstport": 2, "bus": "pci.0"}' \ -device '\{"driver": "ich9-usb-uhci3", "id": "usb1.2", "multifunction": true, "masterbus": "usb1.0", "addr": "0x1d.0x4", "firstport": 4, "bus": "pci.0"}' \ -device '\{"driver": "usb-tablet", "id": "usb-tablet1", "bus": "usb1.0", "port": "1"}' \ -object '\{"qom-type": "iothread", "id": "t1"}' \ -object '\{"qom-type": "iothread", "id": "t2"}' \ -object '\{"qom-type": "iothread", "id": "t3"}' \ -object '\{"qom-type": "iothread", "id": "t4"}' \ -blockdev '\{"node-name": "file_image1", "driver": "file", "auto-read-only": true, "discard": "unmap", "aio": "threads", "filename": "/home/kvm_autotest_root/images/rhel940-64-virtio.qcow2", "cache": {"direct": true, "no-flush": false}}' \ -blockdev '\{"node-name": "drive_image1", "driver": "qcow2", "read-only": false, "cache": {"direct": true, "no-flush": false}, "file": "file_image1"}' \ -device '\{"driver": "virtio-blk-pci", "id": "image1", "drive": "drive_image1", "bootindex": 0, "write-cache": "on", "bus": "pci.0", "addr": "0x3"}' \ -blockdev '\{"node-name": "file_stg0", "driver": "file", "auto-read-only": true, "discard": "unmap", "aio": "native", "filename": "/home/fio/stg0.qcow2", "cache": {"direct": true, "no-flush": false}}' \ -blockdev '\{"node-name": "drive_stg0", "driver": "qcow2", "read-only": false, "cache": {"direct": true, "no-flush": false}, "file": "file_stg0"}' \ -device '\{"driver": "virtio-blk-pci", "id": "stg0", "drive": "drive_stg0", "bootindex": 1, "write-cache": "on", "serial": "stg0", "bus": "pci.0", "addr": "0x4"}' \ -blockdev '\{"node-name": "file_stg1", "driver": "file", "auto-read-only": true, "discard": "unmap", "aio": "native", "filename": "/home/fio/stg1.qcow2", "cache": {"direct": true, "no-flush": false}}' \ -blockdev '\{"node-name": "drive_stg1", "driver": "qcow2", "read-only": false, "cache": {"direct": true, "no-flush": false}, "file": "file_stg1"}' \ -device '\{"driver": "virtio-blk-pci", "id": "stg1", "drive": "drive_stg1", "bootindex": 2, "write-cache": "on", "serial": "stg1", "bus": "pci.0", "addr": "0x5", "iothread-vq-mapping": [{"iothread": "t1"}]}' \ -blockdev '\{"node-name": "file_stg2", "driver": "file", "auto-read-only": true, "discard": "unmap", "aio": "native", "filename": "/home/fio/stg2.qcow2", "cache": {"direct": true, "no-flush": false}}' \ -blockdev '\{"node-name": "drive_stg2", "driver": "qcow2", "read-only": false, "cache": {"direct": true, "no-flush": false}, "file": "file_stg2"}' \ -device '\{"driver": "virtio-blk-pci", "id": "stg2", "drive": "drive_stg2", "bootindex": 3, "write-cache": "on", "serial": "stg2", "bus": "pci.0", "addr": "0x6", "iothread-vq-mapping": [{"iothread": "t1"}, \{"iothread": "t2"}]}' \ -blockdev '\{"node-name": "file_stg3", "driver": "file", "auto-read-only": true, "discard": "unmap", "aio": "native", "filename": "/home/fio/stg3.qcow2", "cache": {"direct": true, "no-flush": false}}' \ -blockdev '\{"node-name": "drive_stg3", "driver": "qcow2", "read-only": false, "cache": {"direct": true, "no-flush": false}, "file": "file_stg3"}' \ -device '\{"driver": "virtio-blk-pci", "id": "stg3", "drive": "drive_stg3", "bootindex": 4, "write-cache": "on", "serial": "stg3", "bus": "pci.0", "addr": "0x7", "iothread-vq-mapping": [{"iothread": "t1"}, \{"iothread": "t2"}, \{"iothread": "t3"}, \{"iothread": "t4"}]}' \ -device '\{"driver": "virtio-net-pci", "mac": "9a:1f:5a:98:ab:db", "id": "idSJRi2K", "netdev": "idHugO6c", "bus": "pci.0", "addr": "0x8"}' \ -netdev  '\{"id": "idHugO6c", "type": "tap", "vhost": true"}'  \ -vnc :0  \ -rtc base=utc,clock=host,driftfix=slew  \ -boot menu=off,order=cdn,once=c,strict=off \ -enable-kvm 2. execute FIO one by one on those disks fio --runtime=30 --group_reporting --cpus_allowed=0-7 --cpus_allowed_policy=split --numjobs=8 --direct=1 --filename=/dev/vdb --ioengine=libaio --size=3G --randrepeat=1 --bs=4k --output-format=json --stonewall --name=randrw-4k-8 --rw=randrw --iodepth=8 (vdc,vdd,vde) 3. run steps 2 10 times Expected results The disk with iothread should get better performance than without iothread Actual results performance with iothread is worse than without Test result Disk-compare IOPS IOPS ----------------------------------------------------------------------------------- stg0-stg1: randrw-4k-8 : 170085 150955 (ratio: 112.7%) (gap: -11.2%) stg1-stg2: randrw-4k-8 : 150955 150424 (ratio: 100.4%) (gap: -0.4 %) stg2-stg3: randrw-4k-8 : 150424 151783 (ratio: 99.1 %) (gap: 0.9 %)

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Resolution

Unresolved