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


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 PREEMPT_COUNT
	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.

endchoice

config PREEMPT_COUNT
       bool
Commit	Line	Data
cc19ca86	1
f8cbd99b IM	2	choice
	3	prompt "Preemption Model"
	4	default PREEMPT_NONE
	5
	6	config PREEMPT_NONE
	7	bool "No Forced Preemption (Server)"
	8	help
	9	This is the traditional Linux preemption model, geared towards
	10	throughput. It will still provide good latencies most of the
	11	time, but there are no guarantees and occasional longer delays
	12	are possible.
	13
	14	Select this option if you are building a kernel for a server or
	15	scientific/computation system, or if you want to maximize the
	16	raw processing power of the kernel, irrespective of scheduling
	17	latencies.
	18
	19	config PREEMPT_VOLUNTARY
	20	bool "Voluntary Kernel Preemption (Desktop)"
87a4c375	21	depends on !ARCH_NO_PREEMPT
cc19ca86	22	help
f8cbd99b IM	23	This option reduces the latency of the kernel by adding more
	24	"explicit preemption points" to the kernel code. These new
	25	preemption points have been selected to reduce the maximum
	26	latency of rescheduling, providing faster application reactions,
3dde6ad8	27	at the cost of slightly lower throughput.
f8cbd99b IM	28
	29	This allows reaction to interactive events by allowing a
	30	low priority process to voluntarily preempt itself even if it
	31	is in kernel mode executing a system call. This allows
	32	applications to run more 'smoothly' even when the system is
cc19ca86 IM	33	under load.
cc19ca86 IM	34
f8cbd99b IM	35	Select this if you are building a kernel for a desktop system.
	36
	37	config PREEMPT
	38	bool "Preemptible Kernel (Low-Latency Desktop)"
87a4c375	39	depends on !ARCH_NO_PREEMPT
bdd4e85d	40	select PREEMPT_COUNT
e335e3eb	41	select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
f8cbd99b IM	42	help
	43	This option reduces the latency of the kernel by making
	44	all kernel code (that is not executing in a critical section)
	45	preemptible. This allows reaction to interactive events by
	46	permitting a low priority process to be preempted involuntarily
	47	even if it is in kernel mode executing a system call and would
	48	otherwise not be about to reach a natural preemption point.
	49	This allows applications to run more 'smoothly' even when the
3dde6ad8	50	system is under load, at the cost of slightly lower throughput
f8cbd99b IM	51	and a slight runtime overhead to kernel code.
	52
	53	Select this if you are building a kernel for a desktop or
	54	embedded system with latency requirements in the milliseconds
	55	range.
	56
	57	endchoice
cc19ca86	58
bdd4e85d	59	config PREEMPT_COUNT
72367933	60	bool