Install Preempt RT Kernel - gkgkgk1215/else GitHub Wiki

Reference: https://frankaemika.github.io/docs/installation_linux.html

Download the kernel

Install the necessary dependencies:

sudo apt-get update
sudo apt-get install build-essential bc curl ca-certificates gnupg2 libssl-dev lsb-release libelf-dev bison flex dwarves zstd libncurses-dev doxygen libncurses-dev kernel-package devscripts

Check the version of kernel you should install: https://www.kernel.org/pub/linux/kernel/projects/rt/
Check the version of kernel you are currently using: (For ubuntu 20.04.6 LTS, the kernel 5.15.0-67-generic is installed.)

uname -r

Download the source files. For kernel 5.15, use the following bash commands:

cd ~
mkdir kernel && cd rtkernel
curl -SLO https://www.kernel.org/pub/linux/kernel/v5.x/linux-5.9.1.tar.xz
curl -SLO https://www.kernel.org/pub/linux/kernel/v5.x/linux-5.9.1.tar.sign
curl -SLO https://www.kernel.org/pub/linux/kernel/projects/rt/5.9/patch-5.9.1-rt20.patch.xz
curl -SLO https://www.kernel.org/pub/linux/kernel/projects/rt/5.9/patch-5.9.1-rt20.patch.sign

Decompress them with:

xz -d *.xz

Verifying file integrity

You can use gpg2 to verify the .tar archives:

gpg2 --verify linux-*.tar.sign
gpg2 --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 647F28654894E3BD457199BE38DBBDC86092693E
gpg2 --verify linux-*.tar.sign

gpg2 --verify patch-*.patch.sign
gpg2 --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys AD85102A6BE1CDFE9BCA84F36CEF3D27CA5B141E
gpg2 --verify patch-*.patch.sign

Compiling the kernel

tar xf linux-*.tar
cd linux-*/
patch -p1 < ../patch-*.patch
cp -v /boot/config-$(uname -r) .config
make olddefconfig
make menuconfig

The second command brings up a terminal interface in which you can configure the preemption model. Navigate with the arrow keys to General Setup > Preemption Model and select Fully Preemptible Kernel (Real-Time).
After that navigate to Cryptographic API > Certificates for signature checking (at the very bottom of the list) > Provide system-wide ring of trusted keys > Additional X.509 keys for default system keyring
Remove the “debian/canonical-certs.pem” from the prompt and press Ok. Save this configuration to .config and exit the TUI.

make -j$(nproc) deb-pkg

sudo dpkg -i ../linux-headers-*.deb ../linux-image-*.deb

Verifying the new kernel

Restart your system. The Grub boot menu should now allow you to choose your newly installed kernel. To see which one is currently being used, see the output of the uname -a command. It should contain the string PREEMPT RT and the version number you chose. Additionally, /sys/kernel/realtime should exist and contain the the number 1.

Allow a user to set real-time permissions for its processes

sudo addgroup realtime
sudo usermod -a -G realtime $(whoami)

Afterwards, add the following limits to the realtime group in /etc/security/limits.conf:

@realtime soft rtprio 99
@realtime soft priority 99
@realtime soft memlock 102400
@realtime hard rtprio 99
@realtime hard priority 99
@realtime hard memlock 102400

Reboot the system.

Benchmark test

Reference: https://m.blog.naver.com/PostView.nhn?blogId=alice_k106&logNo=221170259817&proxyReferer=https:%2F%2Fwww.google.com%2F

git clone git://git.kernel.org/pub/scm/utils/rt-tests/rt-tests.git
cd rt-tests
git checkout stable/v1.0
sudo apt-get install libnuma-dev
make all
sudo make install
./cyclictest -l100000 -m -n -a0 -t1 -p99 -i400 -h400