preempt_rt.md

Ubuntu 20.04 PREEMPT_RT Patch

Install dependancies

apt-get install build-essential libnuma-dev libncurses5-dev flex bison openssl libssl-dev dkms libelf-dev libudev-dev libpci-dev libiberty-dev autoconf fakeroot dwarves zstd

Create directory to build kernel

mkdir -p ~/kernel
cd -p ~/kernel

Download and extract kernel source

wget https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.15.65.tar.gz
tar -xzf linux-5.15.65.tar.gz

Download and extract patch

wget https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.15/patch-5.15.65-rt49.patch.gz
gunzip patch-5.15.65-rt49.patch.gz

apply patch to kernel source

cd linux-5.15.65
patch -p1 < ../patch-5.15.65-rt49.patch

Copy old config file

cp /boot/config-$(uname -r) .config

Set default yes to old config

yes '' | make oldconfig

Modify config file

make menuconfig

Set config according to follwiong steps

# Enable CONFIG_NO_HZ_FULL
 -> General setup
  -> Timers subsystem
   -> Timer tick handling (Full dynticks system (tickless))
    (X) Full dynticks system (tickless)

# Enable CONFIG_PREEMPT_RT
 -> General Setup
  -> Preemption Model (Fully Preemptible Kernel (Real-Time))
   (X) Fully Preemptible Kernel (Real-Time)

# Set CONFIG_HZ_1000
 -> Processor type and features
  -> Timer frequency (1000 HZ)
   (X) 1000 HZ

# Set CPU_FREQ_DEFAULT_GOV_PERFORMANCE [=y]
 ->  Power management and ACPI options
  -> CPU Frequency scaling
   -> CPU Frequency scaling (CPU_FREQ [=y])
    -> Default CPUFreq governor (<choice> [=y])
     (X) performance

Remove SYSTEM_TRUSTED_KEYS and SYSTEM_REVOCATION_KEYS

scripts/config --set-str SYSTEM_TRUSTED_KEYS ""
scripts/config --set-str SYSTEM_REVOCATION_KEYS ""

make and install kernel

make modules_install
make install 
update-grub