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1 | # SPDX-License-Identifier: GPL-2.0-only | |
2 | ||
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)" | |
22 | depends on !ARCH_NO_PREEMPT | |
23 | help | |
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, | |
28 | at the cost of slightly lower throughput. | |
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 | |
34 | under load. | |
35 | ||
36 | Select this if you are building a kernel for a desktop system. | |
37 | ||
38 | config PREEMPT | |
39 | bool "Preemptible Kernel (Low-Latency Desktop)" | |
40 | depends on !ARCH_NO_PREEMPT | |
41 | select PREEMPTION | |
42 | select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK | |
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 | |
51 | system is under load, at the cost of slightly lower throughput | |
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 | ||
58 | config PREEMPT_RT | |
59 | bool "Fully Preemptible Kernel (Real-Time)" | |
60 | depends on EXPERT && ARCH_SUPPORTS_RT | |
61 | select PREEMPTION | |
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 | ||
75 | endchoice | |
76 | ||
77 | config PREEMPT_COUNT | |
78 | bool | |
79 | ||
80 | config PREEMPTION | |
81 | bool | |
82 | select PREEMPT_COUNT |