[linux-2.6-block.git] / kernel / Kconfig.preempt

# SPDX-License-Identifier: GPL-2.0-only

choice
	prompt "Preemption Model"
	default PREEMPT_NONE

config PREEMPT_NONE
	bool "No Forced Preemption (Server)"
	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
	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 PREEMPTION
	select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
	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 pathes (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
Commit	Line	Data
ec8f24b7	1	# SPDX-License-Identifier: GPL-2.0-only
cc19ca86	2
f8cbd99b IM	3	choice
	4	prompt "Preemption Model"
	5	default PREEMPT_NONE
	6
	7	config PREEMPT_NONE
	8	bool "No Forced Preemption (Server)"
	9	help
	10	This is the traditional Linux preemption model, geared towards
	11	throughput. It will still provide good latencies most of the
	12	time, but there are no guarantees and occasional longer delays
	13	are possible.
	14
	15	Select this option if you are building a kernel for a server or
	16	scientific/computation system, or if you want to maximize the
	17	raw processing power of the kernel, irrespective of scheduling
	18	latencies.
	19
	20	config PREEMPT_VOLUNTARY
	21	bool "Voluntary Kernel Preemption (Desktop)"
87a4c375	22	depends on !ARCH_NO_PREEMPT
cc19ca86	23	help
f8cbd99b IM	24	This option reduces the latency of the kernel by adding more
	25	"explicit preemption points" to the kernel code. These new
	26	preemption points have been selected to reduce the maximum
	27	latency of rescheduling, providing faster application reactions,
3dde6ad8	28	at the cost of slightly lower throughput.
f8cbd99b IM	29
	30	This allows reaction to interactive events by allowing a
	31	low priority process to voluntarily preempt itself even if it
	32	is in kernel mode executing a system call. This allows
	33	applications to run more 'smoothly' even when the system is
cc19ca86 IM	34	under load.
cc19ca86 IM	35
f8cbd99b IM	36	Select this if you are building a kernel for a desktop system.
f8cbd99b IM	37
b8d33498	38	config PREEMPT
f8cbd99b	39	bool "Preemptible Kernel (Low-Latency Desktop)"
87a4c375	40	depends on !ARCH_NO_PREEMPT
b8d33498	41	select PREEMPTION
e335e3eb	42	select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
f8cbd99b IM	43	help
	44	This option reduces the latency of the kernel by making
	45	all kernel code (that is not executing in a critical section)
	46	preemptible. This allows reaction to interactive events by
	47	permitting a low priority process to be preempted involuntarily
	48	even if it is in kernel mode executing a system call and would
	49	otherwise not be about to reach a natural preemption point.
	50	This allows applications to run more 'smoothly' even when the
3dde6ad8	51	system is under load, at the cost of slightly lower throughput
f8cbd99b IM	52	and a slight runtime overhead to kernel code.
	53
	54	Select this if you are building a kernel for a desktop or
	55	embedded system with latency requirements in the milliseconds
	56	range.
	57
a50a3f4b TG	58	config PREEMPT_RT
	59	bool "Fully Preemptible Kernel (Real-Time)"
	60	depends on EXPERT && ARCH_SUPPORTS_RT
b8d33498	61	select PREEMPTION
a50a3f4b TG	62	help
	63	This option turns the kernel into a real-time kernel by replacing
	64	various locking primitives (spinlocks, rwlocks, etc.) with
	65	preemptible priority-inheritance aware variants, enforcing
	66	interrupt threading and introducing mechanisms to break up long
	67	non-preemptible sections. This makes the kernel, except for very
	68	low level and critical code pathes (entry code, scheduler, low
	69	level interrupt handling) fully preemptible and brings most
	70	execution contexts under scheduler control.
	71
	72	Select this if you are building a kernel for systems which
	73	require real-time guarantees.
	74
f8cbd99b	75	endchoice
cc19ca86	76
bdd4e85d	77	config PREEMPT_COUNT
72367933	78	bool
a50a3f4b	79
b8d33498	80	config PREEMPTION
a50a3f4b TG	81	bool
a50a3f4b TG	82	select PREEMPT_COUNT