diff options
Diffstat (limited to 'kernel/Kconfig.preempt')
| -rw-r--r-- | kernel/Kconfig.preempt | 139 |
1 files changed, 136 insertions, 3 deletions
diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt index 3f9c97419f02..da326800c1c9 100644 --- a/kernel/Kconfig.preempt +++ b/kernel/Kconfig.preempt @@ -1,3 +1,18 @@ +# 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 + +config ARCH_HAS_PREEMPT_LAZY + bool choice prompt "Preemption Model" @@ -5,6 +20,8 @@ choice config PREEMPT_NONE bool "No Forced Preemption (Server)" + depends on !PREEMPT_RT + 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 @@ -18,6 +35,9 @@ config PREEMPT_NONE config PREEMPT_VOLUNTARY bool "Voluntary Kernel Preemption (Desktop)" + 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 @@ -35,8 +55,8 @@ config PREEMPT_VOLUNTARY config PREEMPT bool "Preemptible Kernel (Low-Latency Desktop)" - select PREEMPT_COUNT - select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK + 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) @@ -52,7 +72,120 @@ config PREEMPT 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
\ No newline at end of file + 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 |