xref: /openbmc/linux/kernel/Kconfig.preempt (revision 87a4c375995ed8eaa721b08825cf73d0b02b3145)
1cc19ca86SIngo Molnar
2f8cbd99bSIngo Molnarchoice
3f8cbd99bSIngo Molnar	prompt "Preemption Model"
4f8cbd99bSIngo Molnar	default PREEMPT_NONE
5f8cbd99bSIngo Molnar
6f8cbd99bSIngo Molnarconfig PREEMPT_NONE
7f8cbd99bSIngo Molnar	bool "No Forced Preemption (Server)"
8cc19ca86SIngo Molnar	help
9f8cbd99bSIngo Molnar	  This is the traditional Linux preemption model, geared towards
10f8cbd99bSIngo Molnar	  throughput. It will still provide good latencies most of the
11f8cbd99bSIngo Molnar	  time, but there are no guarantees and occasional longer delays
12f8cbd99bSIngo Molnar	  are possible.
13f8cbd99bSIngo Molnar
14f8cbd99bSIngo Molnar	  Select this option if you are building a kernel for a server or
15f8cbd99bSIngo Molnar	  scientific/computation system, or if you want to maximize the
16f8cbd99bSIngo Molnar	  raw processing power of the kernel, irrespective of scheduling
17f8cbd99bSIngo Molnar	  latencies.
18f8cbd99bSIngo Molnar
19f8cbd99bSIngo Molnarconfig PREEMPT_VOLUNTARY
20f8cbd99bSIngo Molnar	bool "Voluntary Kernel Preemption (Desktop)"
21*87a4c375SChristoph Hellwig	depends on !ARCH_NO_PREEMPT
22f8cbd99bSIngo Molnar	help
23f8cbd99bSIngo Molnar	  This option reduces the latency of the kernel by adding more
24f8cbd99bSIngo Molnar	  "explicit preemption points" to the kernel code. These new
25f8cbd99bSIngo Molnar	  preemption points have been selected to reduce the maximum
26f8cbd99bSIngo Molnar	  latency of rescheduling, providing faster application reactions,
273dde6ad8SDavid Sterba	  at the cost of slightly lower throughput.
28f8cbd99bSIngo Molnar
29f8cbd99bSIngo Molnar	  This allows reaction to interactive events by allowing a
30f8cbd99bSIngo Molnar	  low priority process to voluntarily preempt itself even if it
31f8cbd99bSIngo Molnar	  is in kernel mode executing a system call. This allows
32f8cbd99bSIngo Molnar	  applications to run more 'smoothly' even when the system is
33cc19ca86SIngo Molnar	  under load.
34cc19ca86SIngo Molnar
35f8cbd99bSIngo Molnar	  Select this if you are building a kernel for a desktop system.
36f8cbd99bSIngo Molnar
37f8cbd99bSIngo Molnarconfig PREEMPT
38f8cbd99bSIngo Molnar	bool "Preemptible Kernel (Low-Latency Desktop)"
39*87a4c375SChristoph Hellwig	depends on !ARCH_NO_PREEMPT
40bdd4e85dSFrederic Weisbecker	select PREEMPT_COUNT
41e335e3ebSRaghavendra K T	select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
42f8cbd99bSIngo Molnar	help
43f8cbd99bSIngo Molnar	  This option reduces the latency of the kernel by making
44f8cbd99bSIngo Molnar	  all kernel code (that is not executing in a critical section)
45f8cbd99bSIngo Molnar	  preemptible.  This allows reaction to interactive events by
46f8cbd99bSIngo Molnar	  permitting a low priority process to be preempted involuntarily
47f8cbd99bSIngo Molnar	  even if it is in kernel mode executing a system call and would
48f8cbd99bSIngo Molnar	  otherwise not be about to reach a natural preemption point.
49f8cbd99bSIngo Molnar	  This allows applications to run more 'smoothly' even when the
503dde6ad8SDavid Sterba	  system is under load, at the cost of slightly lower throughput
51f8cbd99bSIngo Molnar	  and a slight runtime overhead to kernel code.
52f8cbd99bSIngo Molnar
53f8cbd99bSIngo Molnar	  Select this if you are building a kernel for a desktop or
54f8cbd99bSIngo Molnar	  embedded system with latency requirements in the milliseconds
55f8cbd99bSIngo Molnar	  range.
56f8cbd99bSIngo Molnar
57f8cbd99bSIngo Molnarendchoice
58cc19ca86SIngo Molnar
59bdd4e85dSFrederic Weisbeckerconfig PREEMPT_COUNT
60bdd4e85dSFrederic Weisbecker       bool