Comment 14 for bug 1100843

KS (khsh) wrote :

Few updates from a few tests we ran:

Setup:
hypervisor ==> Ubuntu 12.04.2 LTS
libvirt ===> 0.9.8-2ubuntu17.7
qemu-kvm ===> 1.0+noroms-0ubuntu14.7
storage: NFS exports
Guest VM OS: Ubuntu 12.04.1 LTS

Test 1: Created a new VM and kept it Idle for 60+ hours, then ran Unix benchmark test against it. (NO Live-migration/migration)
Result 1: The performance was NOT affected and the result was the same as a fresh VM.

Test 2: Created a new VM, and perform a "virsh save <domain> <file>" followed by a "virsh restore <file>" on the SAME hypervisor. Then run unix benchmark against it.
Result 2: The VM is AFFECTED (cost to perform system calls degraded by ~21% )

Test 3: Rebooted the affected VM from test (2) and re-ran unix-benchmark tests against it.
Result 3: Performance is back to normal and is identical to a newly created and non-migrated/not-saved VM.

Thus, it seems the problem is also exposed by "saving" the running precise domain (memory pages) to state file followed by a "restore" even on the same hypervisor and not necessarily live-migration to a different host.