[Qemu-devel] [KVM][Kemari]:Kemari slows down the VM user experience

[Harshita]

Hello,

As part of implementing Fault Tolerant solution, we are exploring
Kemari. In the process of understanding it, we tested the branch "next"
of git repository. It is working fine. But, once we trigger sync
command, VM response is very slow for the actions performed.

Observation:
------------
Once sync is started vm is responding slowly. (eg., Mouse operation,
keys pressed are shown on the screen after some delay.)
This behavior continues until sync is completed (eg., killing
guest on the primary or resuming guest on secondary, so that no further
sync), and then the guest responds normally.

Our setup:
----------
Host is KVM enabled Linux.
Tested with both Linux and Windows guests.
NFS is used to share the disk image.

Steps followed:
1. Start VM on primary(node1)
qemu-system-x86_64 -hda "/mnt/vm_disks/vm_shared.disk.xm" -m "750"
-monitor stdio --enable-kvm

2. Start VM on secondary(node2), to accept synchronization
qemu-system-x86_64 -hda "/mnt/vm_disks/vm_shared.disk.xm" -m "750"
-monitor stdio --enable-kvm -incoming kemari:tcp:0:4444

3. Started sync using below command, on primary
migrate -d kemari:tcp:node2:4444

4. 'c' on the virtual terminal of secondary VM to take over completely.

Can you please let us know if anything missing in the setup or any
inputs to improve the situation.

Regards,
Harshita