High CPU in idle Windows guest Hi, I'm running a freshly installed Windows 7 domU on an up-to-date Debian jessie machine running Xen 4.4.1-9. When the Windows machine is idle, I'm seeing upwards of 10% CPU usage from the qemu-system-i386 instance. Other Linux and FreeBSD machines register negligable CPU usage (<0.5%). The server is an HP Proliant DL360 G7. Data from perf attacthed to the process might give the best clues. Any information as to why this processes is comsuming so much CPU would be much appreciated. Regards, Terry. # uname -a Linux xen 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt9-3~deb8u1 (2015-04-24) x86_64 GNU/Linux # lsb_release -a No LSB modules are available. Distributor ID: Debian Description: Debian GNU/Linux 8.0 (jessie) Release: 8.0 Codename: jessie # qemu-system-i386 --version QEMU emulator version 2.1.2 (Debian 1:2.1+dfsg-11), Copyright (c) 2003-2008 Fabrice Bellard # cat win7.cfg name = 'win7' vcpus = '1' memory = '4096' builder = 'hvm' disk = [ '/vms/xen/domains/desk_win7/disk1.img,qcow2,hda,rw', '/vms/xen/domains/desk_win7/disk2.img,qcow2,hdb,rw' ] vfb = [ 'vnc=1,vnclisten="0.0.0.0",sdl=0' ] vif = [ 'mac=00:16:3E:FB:FC:39,bridge=xenbr0' ] serial = 'pty' vnc = 1 vnclisten = '0.0.0.0' sdl = 0 usbdevice = 'mouse' audio = 1 soundhw = 'sb16,es1370' on_poweroff = 'destroy' on_reboot = 'restart' on_crash = 'restart' # /usr/bin/qemu-system-i386 -nodefaults -name desk_win7 -boot order=cda -usb -usbdevice mouse -device rtl8139,id=nic0,netdev=net0,mac=00:16:3e:fb:fc:39 -netdev type=tap,id=net0,ifname=vif12.0-emu,script=no,downscript=no -m 4088 -drive file=/vms/xen/domains/desk_win7/disk1.img,if=ide,index=0,media=disk,format=qcow2,cache=writeback -drive file=/vms/xen/domains/desk_win7/disk2.img,if=ide,index=1,media=disk,format=qcow2,cache=writeback -vnc 0.0.0.0:0,to=99 -display none -device cirrus-vga -global vga.vram_size_mb=8 # top Tasks: 134 total, 1 running, 133 sleeping, 0 stopped, 0 zombie %Cpu(s): 16.6 us, 5.5 sy, 0.0 ni, 0.0 id, 77.9 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem: 354420 total, 348884 used, 5536 free, 184 buffers KiB Swap: 17575932 total, 2642868 used, 14933064 free. 4132 cached Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 12297 root 20 0 6683864 192944 1140 S 20.6 54.4 2:25.51 qemu-syste+ # xen dmesg (XEN) Xen version 4.4.1 (Debian 4.4.1-9) (