Control: retitle -1 kvm uses cpu when guest system with USB devices is idle Control: severity -1 minor Control: tag -1 + confirmed wontfix
19.02.2013 11:39, Alexander Kudrevatykh wrote: > Package: qemu-kvm > Version: 1.1.2+dfsg-5 > Severity: normal > > kvm with debian stable guest uses about 10% cpu on idle > > there is kvm command line from ps output (started from libvirt) > /usr/bin/kvm -S -M pc-1.1 -enable-kvm -m 1024 -smp > 1,sockets=1,cores=1,threads=1 -name cups -uuid > ecfcb338-bd8d-cb88-3f02-7a1e52b13609 -nodefconfig -nodefaults -chardev > socket,id=charmonitor,path=/var/lib/libvirt/qemu/cups.monitor,server,nowait > -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown > -kernel /var/lib/libvirt/qemu/dkb/vmlinuz-2.6.32-5-amd64 -initrd > /var/lib/libvirt/qemu/dkb/initrd.img-2.6.32-5-amd64 -append > root=UUID=398df502-1157-440c-ba88-6ec93d68b490 -device > ich9-usb-ehci1,id=usb,bus=pci.0,addr=0x7 -device > ich9-usb-uhci1,masterbus=usb.0,firstport=0,bus=pci.0,addr=0x8 -device > ich9-usb-uhci2,masterbus=usb.0,firstport=2,bus=pci.0,addr=0x9 -device > ich9-usb-uhci3,masterbus=usb.0,firstport=4,bus=pci.0,addr=0xa -drive > file=/dev/second_volume_group/cups,if=none,id=drive-virtio-disk0,format=raw > -device > virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 > -netdev tap,fd=29,id=hostnet0 -device virtio-net- pci,netd e v > =hostnet0,id=net0,mac=52:54:00:f0:b4:30,bus=pci.0,addr=0x3 -chardev > pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -vnc > 127.0.0.1:0 -vga cirrus -device usb-host,hostbus=1,hostaddr=7,id=hostdev0 > -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6 This is a well-known effect of using USB devices. USB spec requires for the machine to poll devices for (in)activity. So the guest pokes USB devices frequently -- for example for (virtual) mouse/tablet it does that 250 times per second. If we lower this value, guest mouse will be sluggish. There's a more or less workaround in later linux guests, an udev rule that allows qemu-emulated mouse/tablet/keyboard to enter (vurtual) sleep mode when not doing anything (the same as for real hardware), -- this takes care of CPU usage, but it makes mouse react slowly to the first event after some idle time, ie, when it got a chance to enter that sleep mode. Another workaround is to remove USB devices entirely (start the guest without any USB device but with USB bus), and (again, virtually) hot- plug any needed devices when the guest is actually in use (and hot- remove again when it isn't in use). This is how USB works, there's almost nothing else we can do about it. Tagging this bugreport as "wontfix" (and minor, since the bad effect is really minimal) instead of closing it right away - just to prevent other bugreports to be filed about this very issue. Thanks, /mjt -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
