Hello (very fearfully, because I found no list that could be helpful and
this one seems to be for developers...),
I have been trying for a long while now to get my VM machines to perform
well, but I can't seem to get it right. I seem to be suffering from two
issues:
1. remote-viewer / libvirt host uses inefficient codecs to transfer
audio / video
2. virtual machines themselves don't seem to have their graphics
accelerated sufficiently
I proceed to elaborate on both:
*#1 - inefficient codecs*
So I have a number of VMs running under qemu on Ubuntu 18.04. AMD 2700x
+ nvidia 1060 gtx (driver nvidia). qemu 4.2, libvirt 6.0.0. Everything
works fine except accessing the VMs remotely: the slower the connection,
the worse it gets. Running them on 4K monitor - please note the
resolution. Using remmina or virt-viewer, makes no difference.
* on local machine, everything is next to perfect, the only noticeable
quality degradation is video full-screen.
* 1gbit LAN: noticeable delays rendering stuff, video becomes grainy
even when in a small window
* 100 mbit LAN / internet: a full screen refresh can take several seconds
* 20/4 mbit internet: when a full screen refresh is needed, I can
observe the 64x64 squares being rendered across the screen and it
takes multiple seconds. Scrolling an editor window is an operation
that takes patience. Connection useless but for the most urgent
tasks where patience is not an issue. Even X over ssh seems the
better option here.
I compare this to Win10 RDP, which - over the same 20/4 connection -
behaves as if I were at the machine in question, even for full-screen video.
The VMs are all setup thus:
* Display spice: Spice server with everything on default, no OpenGL
* Video VirtIO: model VirtIO, 3D acceleration: yes, heads:2, RAM 128MB
I tried video: QXL, but that one completely hogged my LAN, even at gbit,
delivering little for the bandwidth taken (it was less performant than
VirtIO). Same for running everything on local machine too. It seems it
just continuously grabs frames and transmits them regardless of whether
there's any action or not.
Driver in use for guests is virtio-pci for manjaro (video frames
undistorted, but frames lost depending on bandwidth), qxl for ubuntu
(video frames are chopped up, presumably by algorithm snapping them
partially before transmission). QXL despite the fact that video for the
vm in question is set to VirtIO. May also be a result of my tinkering
but useful for comparison anyway.
I have searched all 'round the place and I did find this thread
<https://spice-devel.freedesktop.narkive.com/m7FY7Dvb/spice-v12-00-26-add-gstreamer-support-for-video-streaming>.
It seems to have been merged, but there are no instructions on how to
modify VM configuration to use H264 instead of MJPEG for video encoding.
*#2 - inadequate graphics acceleration*
Well, I mostly base this one on observed CPU usage. I have noticed on
all my linux guests (Manjaro, Ubuntu) that even moving a window around
the desktop significantly raises CPU usage in the guest. I would venture
to guess one core gets taken by such an endeavor. Playing a video in
browser full screen would take closer to two cores.
It is not much different for Windows guests: running a video or a skype
video session absolutely hogs the CPU. While skype itself takes little
CPU, the overall CPU usage goes toward 80 - 100% on a 6 core VM. The
actual process consuming that CPU is not shown in details pane. Using
Red Hat QXL controller for display adapter on Win10 64-bit.
I have found no solution to this problem.
After a very long time and continuing frustration with the problem, I
turn to you guys in hope of a suggestion on what I'm doing wrong. Just
as gladly I would hear of a setup that is known to perform well, I have
no particular need to resolve my exact issues. Reinstalling the host and
/ or guests is not a problem if a known good configuration will perform
for me too...
Thanks,
Jure
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