Kconfig.preempt (71af75b6929458d85f63c0649dc26d6f4c19729e) Kconfig.preempt (c597bfddc9e9e8a63817252b67c3ca0e544ace26)
1# SPDX-License-Identifier: GPL-2.0-only
2
3choice
4 prompt "Preemption Model"
1# SPDX-License-Identifier: GPL-2.0-only
2
3choice
4 prompt "Preemption Model"
5 default PREEMPT_NONE
5 default PREEMPT_NONE_BEHAVIOUR
6
6
7config PREEMPT_NONE
7config PREEMPT_NONE_BEHAVIOUR
8 bool "No Forced Preemption (Server)"
8 bool "No Forced Preemption (Server)"
9 select PREEMPT_NONE if !PREEMPT_DYNAMIC
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
10 help
11 This is the traditional Linux preemption model, geared towards
12 throughput. It will still provide good latencies most of the
13 time, but there are no guarantees and occasional longer delays
14 are possible.
15
16 Select this option if you are building a kernel for a server or
17 scientific/computation system, or if you want to maximize the
18 raw processing power of the kernel, irrespective of scheduling
19 latencies.
20
20config PREEMPT_VOLUNTARY
21config PREEMPT_VOLUNTARY_BEHAVIOUR
21 bool "Voluntary Kernel Preemption (Desktop)"
22 depends on !ARCH_NO_PREEMPT
22 bool "Voluntary Kernel Preemption (Desktop)"
23 depends on !ARCH_NO_PREEMPT
24 select PREEMPT_VOLUNTARY if !PREEMPT_DYNAMIC
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
25 help
26 This option reduces the latency of the kernel by adding more
27 "explicit preemption points" to the kernel code. These new
28 preemption points have been selected to reduce the maximum
29 latency of rescheduling, providing faster application reactions,
30 at the cost of slightly lower throughput.
31
32 This allows reaction to interactive events by allowing a
33 low priority process to voluntarily preempt itself even if it
34 is in kernel mode executing a system call. This allows
35 applications to run more 'smoothly' even when the system is
36 under load.
37
38 Select this if you are building a kernel for a desktop system.
39
38config PREEMPT
40config PREEMPT_BEHAVIOUR
39 bool "Preemptible Kernel (Low-Latency Desktop)"
40 depends on !ARCH_NO_PREEMPT
41 bool "Preemptible Kernel (Low-Latency Desktop)"
42 depends on !ARCH_NO_PREEMPT
41 select PREEMPTION
42 select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
43 select PREEMPT_DYNAMIC if HAVE_PREEMPT_DYNAMIC
43 select PREEMPT
44 help
45 This option reduces the latency of the kernel by making
46 all kernel code (that is not executing in a critical section)
47 preemptible. This allows reaction to interactive events by
48 permitting a low priority process to be preempted involuntarily
49 even if it is in kernel mode executing a system call and would
50 otherwise not be about to reach a natural preemption point.
51 This allows applications to run more 'smoothly' even when the
52 system is under load, at the cost of slightly lower throughput
53 and a slight runtime overhead to kernel code.
54
55 Select this if you are building a kernel for a desktop or
56 embedded system with latency requirements in the milliseconds
57 range.
58
59config PREEMPT_RT
60 bool "Fully Preemptible Kernel (Real-Time)"
44 help
45 This option reduces the latency of the kernel by making
46 all kernel code (that is not executing in a critical section)
47 preemptible. This allows reaction to interactive events by
48 permitting a low priority process to be preempted involuntarily
49 even if it is in kernel mode executing a system call and would
50 otherwise not be about to reach a natural preemption point.
51 This allows applications to run more 'smoothly' even when the
52 system is under load, at the cost of slightly lower throughput
53 and a slight runtime overhead to kernel code.
54
55 Select this if you are building a kernel for a desktop or
56 embedded system with latency requirements in the milliseconds
57 range.
58
59config PREEMPT_RT
60 bool "Fully Preemptible Kernel (Real-Time)"
61 depends on EXPERT && ARCH_SUPPORTS_RT
61 depends on EXPERT && ARCH_SUPPORTS_RT && !PREEMPT_DYNAMIC
62 select PREEMPTION
63 help
64 This option turns the kernel into a real-time kernel by replacing
65 various locking primitives (spinlocks, rwlocks, etc.) with
66 preemptible priority-inheritance aware variants, enforcing
67 interrupt threading and introducing mechanisms to break up long
68 non-preemptible sections. This makes the kernel, except for very
69 low level and critical code paths (entry code, scheduler, low
70 level interrupt handling) fully preemptible and brings most
71 execution contexts under scheduler control.
72
73 Select this if you are building a kernel for systems which
74 require real-time guarantees.
75
76endchoice
77
62 select PREEMPTION
63 help
64 This option turns the kernel into a real-time kernel by replacing
65 various locking primitives (spinlocks, rwlocks, etc.) with
66 preemptible priority-inheritance aware variants, enforcing
67 interrupt threading and introducing mechanisms to break up long
68 non-preemptible sections. This makes the kernel, except for very
69 low level and critical code paths (entry code, scheduler, low
70 level interrupt handling) fully preemptible and brings most
71 execution contexts under scheduler control.
72
73 Select this if you are building a kernel for systems which
74 require real-time guarantees.
75
76endchoice
77
78config PREEMPT_NONE
79 bool
80
81config PREEMPT_VOLUNTARY
82 bool
83
84config PREEMPT
85 bool
86 select PREEMPTION
87 select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
88
78config PREEMPT_COUNT
79 bool
80
81config PREEMPTION
82 bool
83 select PREEMPT_COUNT
84
85config PREEMPT_DYNAMIC
89config PREEMPT_COUNT
90 bool
91
92config PREEMPTION
93 bool
94 select PREEMPT_COUNT
95
96config PREEMPT_DYNAMIC
86 bool
97 bool "Preemption behaviour defined on boot"
98 depends on HAVE_PREEMPT_DYNAMIC
99 select PREEMPT
100 default y
87 help
88 This option allows to define the preemption model on the kernel
89 command line parameter and thus override the default preemption
90 model defined during compile time.
91
92 The feature is primarily interesting for Linux distributions which
93 provide a pre-built kernel binary to reduce the number of kernel
94 flavors they offer while still offering different usecases.

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101 help
102 This option allows to define the preemption model on the kernel
103 command line parameter and thus override the default preemption
104 model defined during compile time.
105
106 The feature is primarily interesting for Linux distributions which
107 provide a pre-built kernel binary to reduce the number of kernel
108 flavors they offer while still offering different usecases.

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