[vfio-users] cpu usage in guest != cpu usage in host, even with exclusive pinning

[Jayme Howard]

Okay wow, Alex.  That made a huge difference immediately.  That dropped me
from 90% to 33% on the main thread, and all the children are below 10%.

On Sun, Apr 3, 2016 at 8:07 PM, Alex Williamson <alex.l.williamson at gmail.com
> wrote:

> If this is the issue I think it is, the unraid folks bisected this and
> found the culprit as:
>
> aca6ff2 KVM: dynamic halt-polling
>
> (
> https://github.com/torvalds/linux/commit/aca6ff29c4063a8d467cdee241e6b3bf7dc4a171
> )
>
> It seems to be a poor interaction of the halt polling interval vs the
> timer ticks on win10.  You can pick a different polling interval with the
> kvm module option halt_poll_ns.  The default is 500000.  It seemed that
> setting this to 400000 or lower resolves the issue.  You can do this via a
> modprobe entry, 'options kvm halt_poll_ns=400000' or on the kernel command
> line with kvm.halt_poll_ns=400000.  You can also change it dynamically via
> 'echo 400000 > /sys/module/kvm/parameters/halt_poll_ns'
>
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