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Add a new entry to the preemption menu which enables the real-time support for the kernel. The choice is only enabled when an architecture supports it. It selects PREEMPT as the RT features depend on it. To achieve that the existing PREEMPT choice is renamed to PREEMPT_LL which select PREEMPT as well. No functional change. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Acked-by: Clark Williams <williams@redhat.com> Acked-by: Daniel Bristot de Oliveira <bristot@redhat.com> Acked-by: Frederic Weisbecker <frederic@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Marc Zyngier <marc.zyngier@arm.com> Acked-by: Daniel Wagner <wagi@monom.org> Acked-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com> Acked-by: Julia Cartwright <julia@ni.com> Acked-by: Tom Zanussi <tom.zanussi@linux.intel.com> Acked-by: Gratian Crisan <gratian.crisan@ni.com> Acked-by: Sebastian Siewior <bigeasy@linutronix.de> Cc: Andrew Morton <akpm@linuxfoundation.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1907172200190.1778@nanos.tec.linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
83 lines
3.0 KiB
Plaintext
83 lines
3.0 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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choice
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prompt "Preemption Model"
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default PREEMPT_NONE
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config PREEMPT_NONE
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bool "No Forced Preemption (Server)"
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help
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This is the traditional Linux preemption model, geared towards
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throughput. It will still provide good latencies most of the
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time, but there are no guarantees and occasional longer delays
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are possible.
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Select this option if you are building a kernel for a server or
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scientific/computation system, or if you want to maximize the
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raw processing power of the kernel, irrespective of scheduling
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latencies.
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config PREEMPT_VOLUNTARY
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bool "Voluntary Kernel Preemption (Desktop)"
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depends on !ARCH_NO_PREEMPT
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help
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This option reduces the latency of the kernel by adding more
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"explicit preemption points" to the kernel code. These new
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preemption points have been selected to reduce the maximum
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latency of rescheduling, providing faster application reactions,
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at the cost of slightly lower throughput.
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This allows reaction to interactive events by allowing a
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low priority process to voluntarily preempt itself even if it
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is in kernel mode executing a system call. This allows
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applications to run more 'smoothly' even when the system is
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under load.
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Select this if you are building a kernel for a desktop system.
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config PREEMPT_LL
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bool "Preemptible Kernel (Low-Latency Desktop)"
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depends on !ARCH_NO_PREEMPT
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select PREEMPT
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select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
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help
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This option reduces the latency of the kernel by making
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all kernel code (that is not executing in a critical section)
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preemptible. This allows reaction to interactive events by
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permitting a low priority process to be preempted involuntarily
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even if it is in kernel mode executing a system call and would
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otherwise not be about to reach a natural preemption point.
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This allows applications to run more 'smoothly' even when the
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system is under load, at the cost of slightly lower throughput
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and a slight runtime overhead to kernel code.
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Select this if you are building a kernel for a desktop or
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embedded system with latency requirements in the milliseconds
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range.
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config PREEMPT_RT
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bool "Fully Preemptible Kernel (Real-Time)"
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depends on EXPERT && ARCH_SUPPORTS_RT
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select PREEMPT
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help
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This option turns the kernel into a real-time kernel by replacing
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various locking primitives (spinlocks, rwlocks, etc.) with
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preemptible priority-inheritance aware variants, enforcing
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interrupt threading and introducing mechanisms to break up long
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non-preemptible sections. This makes the kernel, except for very
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low level and critical code pathes (entry code, scheduler, low
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level interrupt handling) fully preemptible and brings most
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execution contexts under scheduler control.
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Select this if you are building a kernel for systems which
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require real-time guarantees.
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endchoice
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config PREEMPT_COUNT
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bool
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config PREEMPT
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bool
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select PREEMPT_COUNT
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