[vfio-users] Stutter in games

[Laszlo Ersek]

On 01/23/17 20:02, Alex Williamson wrote:

> isolcpus
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/admin-guide/kernel-parameters.txt#n1669

BTW, do you know a method to massage isolcpus without a host reboot? The
last paragraph of the linked section doesn't look promising ("... can
cause problems and suboptimal load balancer performance").

Sometimes the same host is temporarily dedicated to run a VM where
latency doesn't matter much, but throughput does (example: distcc server
with assigned 1Gbit NIC VF); and sometimes the host is dedicated to a VM
where isolcpus would be beneficial to latency (example: interactive 3D
stuff with assigned GPU).

It's quite a pain to reboot the host just to switch between these two;
that sort of eliminates the benefits of virtualization. Furthermore,

- the LUKS password for the host needs to be entered again,
- startup of guests with bridged virtual NICs has to await host DHCP for
internet connectivity again,
- for remote management with virt-manager, the multiplexing SSH master
process on the client has to be re-launched (and then virt-manager has
to be reconnected over the local muxer socket),
- etc

Thanks,
Laszlo