# download 4.14 kernel
wget --continue https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.14.tar.xz

# download 4.14 -> 4.14.27 stable kernel patch
wget --continue https://cdn.kernel.org/pub/linux/kernel/v4.x/patch-4.14.27.xz

# download 4.14.27 -> 4.14.27-rt21 realtime kernel patch
wget --continue https://www.kernel.org/pub/linux/kernel/projects/rt/4.14/older/patch-4.14.27-rt21.patch.xz

# unpack 4.14 kernel
tar xJf linux-4.14.tar.xz

# apply 4.14.27 stable kernel patch
xzcat patch-4.14.27.xz | patch -p 1 -d linux-4.14

# apply 4.14.27-rt21 realtime kernel patch
xzcat patch-4.14.27-rt21.patch.xz | patch -p 1 -d linux-4.14


#
# kernel options to be aware of
#
# (must be set to activate all realtime features)
# CONFIG_PREEMPT_RT_FULL
#
# (disable prio99 watchdog debug tasks, unless really needed/wanted)
# CONFIG_LOCKUP_DETECTOR
# CONFIG_DETECT_HUNG_TASK
#
# (reduced power, but greater latencies, disable it)
# (use CONFIG_100_HZ and CONFIG_HZ_PERIODIC instead)
# CONFIG_NO_HZ
#
# (additional NOPs inserted to each function, ok to enable so you have ftrace)
# CONFIG_FTRACE
#
# (reduced power, but greater latencies, disable appropriately)
# CONFIG_CPU_IDLE
#
# (may cause very large overheads and latencies, disable appropriately)
# CONFIG_DEBUG_*
#
# (make sure these are enabled, but only use "performance")
# CONFIG_CPU_FREQ_GOV_*
# CONFIG_CPU_FREQ_DEFAULT_*
#
# (causes unnecessary processing, for systems that do not need it,
#  disable if not needed)
# CONFIG_HIGHMEM
#