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** Changed in: qemu
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https://bugs.launchpad.net/bugs/1794285
Title:
100% Host CPU usage while guest idling
Status in QEMU:
Incomplete
Bug description:
Hi,
We have an appliance that runs a FreeBSD guest on a Yocto-based host via
qemu-system-x86_64.
Everything functions fine however the host uses n00% of the CPU (where n =
#smp) and RAM allocated to it whilst the 1 guest is sat nearing idle.
Host:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4406 root 20 0 16.7g 16g 26m S 500 53.0 17958:38 qemu-system-x86
Guest:
CPU 0: 0.0% user, 0.0% nice, 0.4% system, 0.0% interrupt, 99.6% idle
CPU 1: 0.0% user, 0.0% nice, 0.4% system, 0.0% interrupt, 99.6% idle
CPU 2: 0.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 100% idle
CPU 3: 0.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 100% idle
CPU 4: 0.4% user, 0.0% nice, 0.0% system, 0.0% interrupt, 99.6% idle
Mem: 43M Active, 4783M Inact, 1530M Wired, 911M Buf, 9553M Free
Swap: 3072M Total, 3072M Free
I have logged this with the appliance vendor and received the response:
"This is expected behaviour and you will see the same in any case where a
Guest OS runs over a Host OS.
Host here has 5 CPUs and it has assigned all of them to Guest.
Since the Host is not being shared by any Guest OS; you will always see the
500% (or the 5 CPUs) given to qemu-system-x86.
I do see the same in lab and is very much expected"
This feels fundamentally wrong to me.
I'm somewhat limited by what can be tested due to the nature of this being an
appliance rather than a mainstream distro.
I'm looking for feedback that I can use to push the vendor into
investigating this issue.
Versions below.
Many thanks,
Gareth
Host:
Linux 204a-node 3.10.100-ovp-rt110-WR6.0.0.31_preempt-rt #1 SMP Fri
Aug 3 01:59:01 PDT 2018 x86_64 x86_64 x86_64 GNU/Linux
Qemu:
QEMU emulator version 1.7.2, Copyright (c) 2003-2008 Fabrice Bellard
Command:
(Vendor identifying information has been removed)
/usr/bin/qemu-system-x86_64 \
-name REMOVED \
-S \
-machine pc-i440fx-1.7,accel=kvm,usb=off \
-m 16384 \
-realtime mlock=on \
-smp 5,sockets=5,cores=1,threads=1 \
-uuid 76277b29-3bd4-4dd4-a705-ed34d6449d6d \
-nographic \
-no-user-config \
-nodefaults \
-chardev
socket,id=charmonitor,path=/var/lib/libvirt/qemu/REMOVED.monitor,server,nowait \
-mon chardev=charmonitor,id=monitor,mode=control \
-rtc base=utc \
-no-shutdown \
-boot strict=on \
-device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 \
-device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x17 \
-netdev tap,fd=22,id=hostnet0,vhost=on,vhostfd=23 \
-device
virtio-net-pci,netdev=hostnet0,id=net0,mac=REMOVED,bus=pci.0,addr=0x11 \
-netdev
tap,ifname=tap1,script=/etc/vehostd/XXX-em3-ifup,id=hostnet1,vhost=on,vhostfd=24
\
-device
virtio-net-pci,netdev=hostnet1,id=net1,mac=REMOVED,bus=pci.0,addr=0x12 \
-netdev
tap,ifname=tap2,script=/etc/vehostd/REMOVED-em4-ifup-SUMMIT,id=hostnet2,vhost=on,vhostfd=25
\
-device
virtio-net-pci,netdev=hostnet2,id=net2,mac=REMOVED,bus=pci.0,addr=0x1c \
-netdev
tap,ifname=tap3,script=/etc/vehostd/REMOVED-em4-re-re-ifup,id=hostnet3,vhost=on,vhostfd=26
\
-device
virtio-net-pci,netdev=hostnet3,id=net3,mac=REMOVED,bus=pci.0,addr=0x1d \
-chardev pty,id=charserial0 \
-device isa-serial,chardev=charserial0,id=serial0 \
-chardev tty,id=charserial1,path=/dev/ttyS1 \
-device isa-serial,chardev=charserial1,id=serial1 \
-chardev tty,id=charserial2,path=/dev/ttyS2 \
-device isa-serial,chardev=charserial2,id=serial2 \
-chardev tty,id=charserial3,path=/dev/ttyS3 \
-device isa-serial,chardev=charserial3,id=serial3 \
-device i6300esb,id=watchdog0,bus=pci.0,addr=0x10 \
-watchdog-action reset \
-object rng-random,id=rng0,filename=/dev/random \
-device
virtio-rng-pci,rng=rng0,max-bytes=1024,period=2000,bus=pci.0,addr=0x1e \
-smbios type=0,vendor="INSYDE
Corp.",version=REMOVED,date=11/03/2017,release=1.00 \
-smbios
type=1,manufacturer=REMOVED,product=REMOVED,version=REMOVED,serial=VF-NET \
-device REMOVED-pci,host=0000:1c:00.0 \
-device kvm-pci-assign,host=0000:00:14.0 \
-device pci-hgcommdev,vmindex=0,bus=pci.0,addr=0x16 \
-drive
file=/REMOVED/REMOVED-current.img,if=none,id=drive-virtio-disk0,format=raw,cache=directsync,aio=native
\
-device
virtio-blk-pci,scsi=off,bus=pci.0,addr=0x13,drive=drive-virtio-disk0,id=virtio-disk0,config-wce=off,x-data-plane=on,bootindex=1
\
-drive
file=/REMOVED/REMOVED-var-config.img,if=none,id=drive-virtio-disk1,format=raw,cache=directsync,aio=native
\
-device
virtio-blk-pci,scsi=off,bus=pci.0,addr=0x15,drive=drive-virtio-disk1,id=virtio-disk1,config-wce=off,x-data-plane=on,bootindex=-1
\
-drive
file=/REMOVED/REMOVED-aux-disk.img,if=none,id=drive-ide0-0-1,format=raw,cache=directsync,discard=unmap
\
-device ide-hd,bus=ide.0,unit=1,drive=drive-ide0-0-1,id=ide0-0-1,bootindex=-1
\
-drive
file=/REMOVED/images/0/REMOVED-platform.img,if=none,id=drive-ide1-0-1,format=raw,cache=directsync,discard=unmap
\
-device ide-hd,bus=ide.1,unit=1,drive=drive-ide1-0-1,id=ide1-0-1,bootindex=-1
\
-msg timestamp=on
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