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| -rw-r--r-- | kernel/Kconfig.preempt | 136 |
1 files changed, 136 insertions, 0 deletions
diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt new file mode 100644 index 0000000000..c2f1fd95a8 --- /dev/null +++ b/kernel/Kconfig.preempt @@ -0,0 +1,136 @@ +# SPDX-License-Identifier: GPL-2.0-only + +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 + +choice + prompt "Preemption Model" + default PREEMPT_NONE + +config PREEMPT_NONE + bool "No Forced Preemption (Server)" + 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_NO_PREEMPT + 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 + 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_RT + bool "Fully Preemptible Kernel (Real-Time)" + depends on EXPERT && ARCH_SUPPORTS_RT + 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. + +endchoice + +config PREEMPT_COUNT + bool + +config PREEMPTION + bool + select PREEMPT_COUNT + +config PREEMPT_DYNAMIC + bool "Preemption behaviour defined on boot" + depends on HAVE_PREEMPT_DYNAMIC && !PREEMPT_RT + 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. + + |