[fedora-virt] possible memory leak ?

[Razvan Radu]

hello,

after running an stress program in the guest for 6 to 24 hours the 
qemu-kvm process uses up all the available memory and gets killed by 
oom, is this an bug or an configuration problem ?

host:
arch: intel i7 12gb ram
fedora 12 updated as of 2010-04-19 with fedora-virt packages
kernel: 2.6.32.11-99.fc12.x86_64
qemu: qemu*0.12.3-7.fc12.x86_64, also tested with qemu*0.12.3-6.fc12.x86_64
libvirt: libvirt*0.7.7-2.fc12.x86_64
qemu command: /usr/bin/qemu-kvm -S -M pc-0.11 -enable-kvm -m 3072 -smp 
4,sockets=4,cores=1,threads=1 -name guest-00574 -uuid 
3f26c499-b029-3e1c-2410-fd197b262057 -nodefaults -chardev 
socket,id=monitor,path=/var/lib/libvirt/qemu/guest-00574.monitor,server,nowait 
-mon chardev=monitor,mode=readline -rtc base=utc -boot dc -drive 
if=none,media=cdrom,id=drive-ide0-1-0 -device 
ide-drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -drive 
file=/dev/hdd.img/guest-00574-1,if=none,id=drive-virtio-disk0,boot=on,cache=none 
-device 
virtio-blk-pci,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0 
-device 
virtio-net-pci,vlan=0,id=net0,mac=54:52:00:00:00:49,bus=pci.0,addr=0x5 
-net tap,fd=21,vlan=0,name=hostnet0 -usb -device usb-tablet,id=input0 
-vnc 0.0.0.0:2 -vga cirrus -device 
virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3

guest:
CentOS release 5.4
kernel: 2.6.18-164.15.1.el5

stress program:
http://weather.ou.edu/~apw/projects/stress/
comman line: ./stress -v -c 4 -m 4 --vm-bytes 800M -d 4 --hdd-bytes 100M 
-t 100000


the qemu process is constantly using more and more memory and after a 
while it get killed
I have tested with:
- no hugepages
- hugepages
- lvm
- qcow2 image files
- cache=writeback
- cache=none
all resulted in the same memory usage pattern (slowly growing)


do you know of an formula for calculating the memory overhead for 
qemu-kvm (without an potential memory leak ...) ?
I have noticed an 20% overhead with and without hugepages (pmap reported 
a total of 1.2G for an 1G guest and 3.6G total for an 3G guest)
is 20% an correct assumption (it seems a little high) ?
I have observed the same overhead with hugepages, is this normal ?


thanks,

-- 
Razvan RADU
+40 (72) 7772218 / mobile