[vfio-users] Calling ALL VM experts - Seeking assistance with AMD FX CPUs

[Alyx]

Hopefully this reply works.
So. I have an FX-8350. I have the exact issue as described, and believe the
person he was talking about.

Here's my config - http://pastebin.com/McuiqyDt
Note that the above config is just the one I am running just now and has
some options that have no effect, such as "vmport=off", in a desperation
attempt to see if any option makes a difference.

So I've tried many things to get the stuttering to subside. I've tried,
changing the kernel tick-rate, changing to a realtime kernel, changing to
the CK kernel (with the belief that a different I/O scheduler might solve
it), making the VM BIOS, changing the pre-emptive state of the kernel,
changing the PCIE slot of the GPU (so that it is now in slot 1, and the
"main" GPU in slot 2), isolating cores, hugepages, moving threads via cset.
And of course a combination of all of the above. The only thing that sort
of solves it if I reduce the number of cores I pass to the VM, more than 4
and it increases the stuttering, and less than 4 makes it not really
powerful enough for higher-end gaming.

There was a random thought that it could've been something to do with the
shared FPU, however after isolating the last 6 cores and only passing every
second core (3, 5, 7) so that they are on separate FPU modules (meaning
that it's "pair" is not doing any work at all), yields the same results as
passing 3 cores normally.

I would describe the issue as a stuttering of sorts, where the game freezes
and then suddenly speeds up to catch back up to realtime (sound usually
works as normal during the stutter as if nothing happened). It's fine
within a desktop environment and when doing benchmarks such as Cinebench
and Unigine-Heaven (Heaven being exactly the same as bare metal). However
it's when I move into a more game-like situation such as 3D Mark's
benchmarks where the stuttering appears. Some 3D Mark benchmarks can even
cause the VM/Program to freeze such as the API overhead test which also
displays a large amount of stuttering during the test (assuming it doesn't
crash half way though of course). Another program-specific issue is that
the program HWINFO also locks up the entire VM when it tries to detect the
CPU (works on Intel hardware) causing Windows to shut down after a ~10
seconds. Sure the HWINFO isn't too much of an issue, but it could be
related.
The stuttering becomes more apparent as the game tries to load in textures,
for example exiting out of a safe area into a large open world (Game: The
Division) causes huge amounts of stuttering until everything has finished
"popping-in". However, once everything has loaded in, if I look at the
frametimes in MSI Afterburner I can see that it varies dramatically, so
I'll be at 60 FPS and see the frametimes jump from low ~20ms to 100ms+ with
no "big" stuttering like when the textures are loading.

Any help is appreciated and I'll try any suggestions at this point
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