[vfio-users] Stutter in games

Scott shewless at unleashed-web.org
Mon Jan 23 21:47:49 UTC 2017


You did the msi interrupt thing for hdmi audio right?

scott

On Jan 23, 2017 3:34 PM, "Alex Williamson" <alex.l.williamson at gmail.com>
wrote:

> On Mon, Jan 23, 2017 at 12:50 PM, Laszlo Ersek <lersek at redhat.com> wrote:
>
>> 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
>>
>
> No need to sell me on it, I agree it'd be useful.  I imagine there's some
> way to do this with cgroups, ie. dynamically add/remove cpus from the
> default init process cpuset, but it hasn't nagged at me enough to find time
> to investigate further.  It seems like someone had reported a more dynamic
> setup.  Thanks,
>
> Alex
>
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