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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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config PREEMPT_NONE_BUILD bool
config PREEMPT_VOLUNTARY_BUILD bool
config PREEMPT_BUILD bool select PREEMPTION select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
config ARCH_HAS_PREEMPT_LAZY bool
choice prompt "Preemption Model" default PREEMPT_LAZY if ARCH_HAS_PREEMPT_LAZY default PREEMPT_NONE
config PREEMPT_NONE bool "No Forced Preemption (Server)" depends on !PREEMPT_RT depends on ARCH_NO_PREEMPT select PREEMPT_NONE_BUILD if !PREEMPT_DYNAMIC help This is the traditional Linux preemption model, geared towards throughput. It will still provide good latencies most of the time, but there are no guarantees and occasional longer delays are possible.
Select this option if you are building a kernel for a server or scientific/computation system, or if you want to maximize the raw processing power of the kernel, irrespective of scheduling latencies.
config PREEMPT_VOLUNTARY bool "Voluntary Kernel Preemption (Desktop)" depends on !ARCH_HAS_PREEMPT_LAZY depends on !ARCH_NO_PREEMPT depends on !PREEMPT_RT select PREEMPT_VOLUNTARY_BUILD if !PREEMPT_DYNAMIC help This option reduces the latency of the kernel by adding more "explicit preemption points" to the kernel code. These new preemption points have been selected to reduce the maximum latency of rescheduling, providing faster application reactions, at the cost of slightly lower throughput.
This allows reaction to interactive events by allowing a low priority process to voluntarily preempt itself even if it is in kernel mode executing a system call. This allows applications to run more 'smoothly' even when the system is under load.
Select this if you are building a kernel for a desktop system.
config PREEMPT bool "Preemptible Kernel (Low-Latency Desktop)" depends on !ARCH_NO_PREEMPT select PREEMPT_BUILD if !PREEMPT_DYNAMIC help This option reduces the latency of the kernel by making all kernel code (that is not executing in a critical section) preemptible. This allows reaction to interactive events by permitting a low priority process to be preempted involuntarily even if it is in kernel mode executing a system call and would otherwise not be about to reach a natural preemption point. This allows applications to run more 'smoothly' even when the system is under load, at the cost of slightly lower throughput and a slight runtime overhead to kernel code.
Select this if you are building a kernel for a desktop or embedded system with latency requirements in the milliseconds range.
config PREEMPT_LAZY bool "Scheduler controlled preemption model" depends on !ARCH_NO_PREEMPT depends on ARCH_HAS_PREEMPT_LAZY select PREEMPT_BUILD if !PREEMPT_DYNAMIC help This option provides a scheduler driven preemption model that is fundamentally similar to full preemption, but is less eager to preempt SCHED_NORMAL tasks in an attempt to reduce lock holder preemption and recover some of the performance gains seen from using Voluntary preemption.
endchoice
config PREEMPT_RT bool "Fully Preemptible Kernel (Real-Time)" depends on EXPERT && ARCH_SUPPORTS_RT && !COMPILE_TEST select PREEMPTION help This option turns the kernel into a real-time kernel by replacing various locking primitives (spinlocks, rwlocks, etc.) with preemptible priority-inheritance aware variants, enforcing interrupt threading and introducing mechanisms to break up long non-preemptible sections. This makes the kernel, except for very low level and critical code paths (entry code, scheduler, low level interrupt handling) fully preemptible and brings most execution contexts under scheduler control.
Select this if you are building a kernel for systems which require real-time guarantees.
config PREEMPT_RT_NEEDS_BH_LOCK bool "Enforce softirq synchronisation on PREEMPT_RT" depends on PREEMPT_RT help Enforce synchronisation across the softirqs context. On PREEMPT_RT the softirq is preemptible. This enforces the same per-CPU BLK semantic non-PREEMPT_RT builds have. This should not be needed because per-CPU locks were added to avoid the per-CPU BKL.
This switch provides the old behaviour for testing reasons. Select this if you suspect an error with preemptible softirq and want test the old synchronized behaviour.
config PREEMPT_COUNT bool
config PREEMPTION bool select PREEMPT_COUNT
config PREEMPT_DYNAMIC bool "Preemption behaviour defined on boot" depends on HAVE_PREEMPT_DYNAMIC select JUMP_LABEL if HAVE_PREEMPT_DYNAMIC_KEY select PREEMPT_BUILD default y if HAVE_PREEMPT_DYNAMIC_CALL help This option allows to define the preemption model on the kernel command line parameter and thus override the default preemption model defined during compile time.
The feature is primarily interesting for Linux distributions which provide a pre-built kernel binary to reduce the number of kernel flavors they offer while still offering different usecases.
The runtime overhead is negligible with HAVE_STATIC_CALL_INLINE enabled but if runtime patching is not available for the specific architecture then the potential overhead should be considered.
Interesting if you want the same pre-built kernel should be used for both Server and Desktop workloads.
config SCHED_CORE bool "Core Scheduling for SMT" depends on SCHED_SMT help This option permits Core Scheduling, a means of coordinated task selection across SMT siblings. When enabled -- see prctl(PR_SCHED_CORE) -- task selection ensures that all SMT siblings will execute a task from the same 'core group', forcing idle when no matching task is found.
Use of this feature includes: - mitigation of some (not all) SMT side channels; - limiting SMT interference to improve determinism and/or performance.
SCHED_CORE is default disabled. When it is enabled and unused, which is the likely usage by Linux distributions, there should be no measurable impact on performance.
config SCHED_CLASS_EXT bool "Extensible Scheduling Class" depends on BPF_SYSCALL && BPF_JIT && DEBUG_INFO_BTF select STACKTRACE if STACKTRACE_SUPPORT help This option enables a new scheduler class sched_ext (SCX), which allows scheduling policies to be implemented as BPF programs to achieve the following:
- Ease of experimentation and exploration: Enabling rapid iteration of new scheduling policies. - Customization: Building application-specific schedulers which implement policies that are not applicable to general-purpose schedulers. - Rapid scheduler deployments: Non-disruptive swap outs of scheduling policies in production environments.
sched_ext leverages BPF struct_ops feature to define a structure which exports function callbacks and flags to BPF programs that wish to implement scheduling policies. The struct_ops structure exported by sched_ext is struct sched_ext_ops, and is conceptually similar to struct sched_class.
For more information: Documentation/scheduler/sched-ext.rst https://github.com/sched-ext/scx