GPU frequency greatly reduced after suspending, degrading performance significantly

[Leonardo Müller]

It was noticed that the GPU frequency is greatly reduced after waking up from suspension. Normally, the computer GPU's minimum frequency is 300 MHz and the maximum 1000 MHz. When this bug happens, the observed frequency is 100 MHz and multiple kernel WARNINGs appear.

As the system uses Xfce and the screen resolution is 1366x768, for common desktop usage no problem is noticeable, but heavier tasks, as games, are greatly impacted.

Steps to reproduce:

1) Have Intel GVT enabled (i915.enable_gvt=1);
2) Run a guest using Intel GVT-g. A guest command, for example:

/usr/local/bin/qemu-system-x86_64 -name 'Windows 10' -nodefaults -M pc-i440fx-3.1,usb=true -machine kernel_irqchip=on -device qemu-xhci,id=qemu-xhci,addr=4,p2=15,p3=15 -global PIIX4_PM.disable_s3=1 -global PIIX4_PM.disable_s4=1 -hda redm.qcow2 -enable-kvm -cpu Skylake-Client,hv_time,hv_relaxed,hv_vapic,hv_spinlocks=0x1fff,hv_runtime -smp cores=2,threads=2 -m 3072M -bios /usr/local/share/qemu/bios.bin -device usb-tablet,id=tablet,bus=qemu-xhci.0,port=1 -vga none -monitor vc -serial stdio -display gtk,gl=on -device vfio-pci,sysfsdev=/sys/bus/pci/devices/0000:00:02.0/20312cec-80f4-448a-9f09-7b93adbf672c,x-igd-opregion=on,rombar=0,display=on,addr=0x3,id=iHD520 -netdev bridge,id=hostnet0,br=virbr0 -device e1000,netdev=hostnet0,id=net0,mac=aa:bb:cc:dd:ee:11,addr=0x8 -audiodev id=none,driver=none -device ivshmem-plain,memdev=HMB -object memory-backend-file,id=HMB,size=4M,mem-path=/dev/shm/test,share=on

3) Use the guest a bit and then turn off the guest;
4) Suspend the host system;
5) Wake up the host system;
6) Notice how GPU clock is limited to 100 MHz and heavier tasks are greatly degraded.

Processor: Intel Core i3-6100U;
Video: Intel HD Graphics 520;
Architecture: amd64;
RAM memory: 20 GB;
Kernel version: 5.3.0-19-lowlatency;
Distribution: Xubuntu 18.04.3 amd64.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-5.3.0-19-lowlatency 5.3.0-19.20~18.04.2+2
ProcVersionSignature: Ubuntu 5.3.0-19.20~18.04.2-lowlatency 5.3.1
Uname: Linux 5.3.0-19-lowlatency x86_64
ApportVersion: 2.20.9-0ubuntu7.7
Architecture: amd64
CurrentDesktop: XFCE
Date: Mon Oct 28 13:06:25 2019
InstallationDate: Installed on 2017-06-13 (866 days ago)
InstallationMedia: Xubuntu 17.04 "Zesty Zapus" - Release amd64 (20170412)
SourcePackage: linux-signed-hwe-edge
UpgradeStatus: Upgraded to bionic on 2017-10-20 (738 days ago)