[Qemu-devel] balloon stats not working if qemu is started with -machine option

[Alexandre DERUMIER]

Hi,

I have noticed that balloon stats are not working if a qemu guest is started 
with -machine option.

(-machine pc, or any version) . Tested of qemu 1.7,2.1 && 2.2


When the guest is starting (balloon driver not yet loaded)

$VAR1 = {
          'last-update' => 0,
          'stats' => {
                       'stat-free-memory' => -1,
                       'stat-swap-in' => -1,
                       'stat-total-memory' => -1,
                       'stat-major-faults' => -1,
                       'stat-minor-faults' => -1,
                       'stat-swap-out' => -1
                     }
        };


then

when the guest has loaded his driver

$VAR1 = {
          'last-update' => 1425882998,
          'stats' => {
                       'stat-free-memory' => -1,
                       'stat-swap-in' => '4039065379203448832',
                       'stat-total-memory' => -1,
                       'stat-major-faults' => -1,
                       'stat-minor-faults' => -1,
                       'stat-swap-out' => '-6579759055588294656'
                     }
        };

$VAR1 = {
          'last-update' => 1425882998,
          'stats' => {
                       'stat-free-memory' => -1,
                       'stat-swap-in' => '4039065379203448832',
                       'stat-total-memory' => -1,
                       'stat-major-faults' => -1,
                       'stat-minor-faults' => -1,
                       'stat-swap-out' => '-6579759055588294656'
                     }
        };


$VAR1 = {
          'last-update' => 1425882998,
          'stats' => {
                       'stat-free-memory' => -1,
                       'stat-swap-in' => '4039065379203448832',
                       'stat-total-memory' => -1,
                       'stat-major-faults' => -1,
                       'stat-minor-faults' => -1,
                       'stat-swap-out' => '-6579759055588294656'
                     }
        };


It's seem that a some stats are retrieved, but last-update don't increment.
Removing the machine option resolve the problem.


I'm working with proxmox team, and a lot of user have reported balloning bug, 
because we pass the -machine option when are a doing live migration.

I'm surprised that -machine pc also have this bug. (Isn't it supposed to be the 
default machine config ?)




here the sample command line:


/usr/bin/kvm -id 150  -chardev 
socket,id=qmp,path=/var/run/qemu-server/150.qmp,server,nowait -mon 
chardev=qmp,mode=control -vnc unix:/var/run/qemu-server/150.vnc,x509,password 
-pidfile /var/run/qemu-server/150.pid -daemonize -smbios 
type=1,manufacturer=dell,version=1,product=3,uuid=f0686bfb-50b8-4d31-a4cb-b1cf60eeb648
 -name debianok -smp 1,sockets=2,cores=1,maxcpus=2 -nodefaults -boot 
menu=on,strict=on,reboot-timeout=1000 -vga cirrus -cpu 
kvm64,+lahf_lm,+x2apic,+sep -m 4096 -k fr -device 
piix3-usb-uhci,id=uhci,bus=pci.0,addr=0x1.0x2 -device 
usb-tablet,id=tablet,bus=uhci.0,port=1 -device 
virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 -iscsi 
initiator-name=iqn.1993-08.org.debian.01.24b0d01a62a3 -drive 
file=/var/lib/vz/images/150/vm-150-disk-1.raw,if=none,id=drive-virtio0,format=raw,aio=native,cache=none
 -device 
virtio-blk-pci,drive=drive-virtio0,id=virtio0,bus=pci.0,addr=0xa,bootindex=100 
-netdev 
type=tap,id=net0,ifname=tap150i0,script=/var/lib/qemu-server/pve-bridge,downscript=/var/lib/qemu-server/pve-bridgedown,vhost=on
 -device 
virtio-net-pci,mac=76:EF:E9:ED:9D:41,netdev=net0,bus=pci.0,addr=0x12,id=net0,bootindex=300
 -machine pc