If youre running Debian KVM's, i would also recommend using the "cloud" linux kernel from backports (or actual buster). Google Cloud is KVM, so all its optimizations should be of benefit.
https://packages.debian.org/stretch-backports/linux-image-cloud-amd64
Not sure what optimizations Google makes but because I'm cowboy (and because snapshots) I installed the cloud package. I'd really like to know what optimizations they made so I could compare metrics against an untuned machine.
For simple folk like me here's the process:
# Add backports to sources.list:
nano /etc/apt/sources/list
#Stretch Backports
deb
http://ftp.debian.org/debian stretch-backports main contrib main
deb-src
http://ftp.debian.org/debian stretch-backports main contrib main
# Update the sources
apt update
# Install the cloud package
apt install linux-image-cloud-amd64
FYI this also installs apparmor.
Uname -a :
4.19.0-0.bpo.5-cloud-amd64 #1 SMP Debian 4.19.37-3~bpo9+1 (2019-05-18) x86_64 GNU/Linux
This along with other tunables could probably be made into a scipt but I'm still not sure what the ROI will be yet.
