The bug is still exist in version 0.9.12.3-1+deb7u1 # uptime 10:14:03 up 39 days, 16 min, 2 users, load average: 0.24, 0.27, 0.25
# top top - 10:14:32 up 39 days, 17 min, 2 users, load average: 0.20, 0.26, 0.24 Tasks: 106 total, 1 running, 105 sleeping, 0 stopped, 0 zombie %Cpu(s): 1.1 us, 1.1 sy, 0.0 ni, 96.3 id, 1.5 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem: 8196188 total, 8012432 used, 183756 free, 336 buffers KiB Swap: 0 total, 0 used, 0 free, 186404 cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 28184 libvirt- 20 0 4387m 4.0g 840 S 4.4 51.4 7207:43 kvm 2486 root 20 0 2946m 2.6g 3244 S 0.0 33.1 791:16.66 libvirtd 6403 libvirt- 20 0 894m 526m 1176 S 0.7 6.6 393:18.91 kvm 8GB RAM, 4GB allocated to windows-2012-64bit client, 512MB allocated to wheezy-32bit client. And libvirtd used 2.6GB after 39 days up. Almost to crash!