1 # SPDX-License-Identifier: GPL-2.0-only << 2 << 3 config PREEMPT_NONE_BUILD << 4 bool << 5 << 6 config PREEMPT_VOLUNTARY_BUILD << 7 bool << 8 << 9 config PREEMPT_BUILD << 10 bool << 11 select PREEMPTION << 12 select UNINLINE_SPIN_UNLOCK if !ARCH_I << 13 1 14 choice 2 choice 15 prompt "Preemption Model" 3 prompt "Preemption Model" 16 default PREEMPT_NONE 4 default PREEMPT_NONE 17 5 18 config PREEMPT_NONE 6 config PREEMPT_NONE 19 bool "No Forced Preemption (Server)" 7 bool "No Forced Preemption (Server)" 20 select PREEMPT_NONE_BUILD if !PREEMPT_ << 21 help 8 help 22 This is the traditional Linux preemp 9 This is the traditional Linux preemption model, geared towards 23 throughput. It will still provide go 10 throughput. It will still provide good latencies most of the 24 time, but there are no guarantees an 11 time, but there are no guarantees and occasional longer delays 25 are possible. 12 are possible. 26 13 27 Select this option if you are buildi 14 Select this option if you are building a kernel for a server or 28 scientific/computation system, or if 15 scientific/computation system, or if you want to maximize the 29 raw processing power of the kernel, 16 raw processing power of the kernel, irrespective of scheduling 30 latencies. 17 latencies. 31 18 32 config PREEMPT_VOLUNTARY 19 config PREEMPT_VOLUNTARY 33 bool "Voluntary Kernel Preemption (Des 20 bool "Voluntary Kernel Preemption (Desktop)" 34 depends on !ARCH_NO_PREEMPT << 35 select PREEMPT_VOLUNTARY_BUILD if !PRE << 36 help 21 help 37 This option reduces the latency of t 22 This option reduces the latency of the kernel by adding more 38 "explicit preemption points" to the 23 "explicit preemption points" to the kernel code. These new 39 preemption points have been selected 24 preemption points have been selected to reduce the maximum 40 latency of rescheduling, providing f 25 latency of rescheduling, providing faster application reactions, 41 at the cost of slightly lower throug 26 at the cost of slightly lower throughput. 42 27 43 This allows reaction to interactive 28 This allows reaction to interactive events by allowing a 44 low priority process to voluntarily 29 low priority process to voluntarily preempt itself even if it 45 is in kernel mode executing a system 30 is in kernel mode executing a system call. This allows 46 applications to run more 'smoothly' 31 applications to run more 'smoothly' even when the system is 47 under load. 32 under load. 48 33 49 Select this if you are building a ke 34 Select this if you are building a kernel for a desktop system. 50 35 51 config PREEMPT 36 config PREEMPT 52 bool "Preemptible Kernel (Low-Latency 37 bool "Preemptible Kernel (Low-Latency Desktop)" 53 depends on !ARCH_NO_PREEMPT !! 38 select PREEMPT_COUNT 54 select PREEMPT_BUILD !! 39 select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK 55 help 40 help 56 This option reduces the latency of t 41 This option reduces the latency of the kernel by making 57 all kernel code (that is not executi 42 all kernel code (that is not executing in a critical section) 58 preemptible. This allows reaction t 43 preemptible. This allows reaction to interactive events by 59 permitting a low priority process to 44 permitting a low priority process to be preempted involuntarily 60 even if it is in kernel mode executi 45 even if it is in kernel mode executing a system call and would 61 otherwise not be about to reach a na 46 otherwise not be about to reach a natural preemption point. 62 This allows applications to run more 47 This allows applications to run more 'smoothly' even when the 63 system is under load, at the cost of 48 system is under load, at the cost of slightly lower throughput 64 and a slight runtime overhead to ker 49 and a slight runtime overhead to kernel code. 65 50 66 Select this if you are building a ke 51 Select this if you are building a kernel for a desktop or 67 embedded system with latency require 52 embedded system with latency requirements in the milliseconds 68 range. 53 range. 69 54 70 config PREEMPT_RT << 71 bool "Fully Preemptible Kernel (Real-T << 72 depends on EXPERT && ARCH_SUPPORTS_RT << 73 select PREEMPTION << 74 help << 75 This option turns the kernel into a << 76 various locking primitives (spinlock << 77 preemptible priority-inheritance awa << 78 interrupt threading and introducing << 79 non-preemptible sections. This makes << 80 low level and critical code paths (e << 81 level interrupt handling) fully pree << 82 execution contexts under scheduler c << 83 << 84 Select this if you are building a ke << 85 require real-time guarantees. << 86 << 87 endchoice 55 endchoice 88 56 89 config PREEMPT_COUNT 57 config PREEMPT_COUNT 90 bool !! 58 bool 91 << 92 config PREEMPTION << 93 bool << 94 select PREEMPT_COUNT << 95 << 96 config PREEMPT_DYNAMIC << 97 bool "Preemption behaviour defined on << 98 depends on HAVE_PREEMPT_DYNAMIC && !PR << 99 select JUMP_LABEL if HAVE_PREEMPT_DYNA << 100 select PREEMPT_BUILD << 101 default y if HAVE_PREEMPT_DYNAMIC_CALL << 102 help << 103 This option allows to define the pre << 104 command line parameter and thus over << 105 model defined during compile time. << 106 << 107 The feature is primarily interesting << 108 provide a pre-built kernel binary to << 109 flavors they offer while still offer << 110 << 111 The runtime overhead is negligible w << 112 but if runtime patching is not avail << 113 then the potential overhead should b << 114 << 115 Interesting if you want the same pre << 116 both Server and Desktop workloads. << 117 << 118 config SCHED_CORE << 119 bool "Core Scheduling for SMT" << 120 depends on SCHED_SMT << 121 help << 122 This option permits Core Scheduling, << 123 selection across SMT siblings. When << 124 prctl(PR_SCHED_CORE) -- task selecti << 125 will execute a task from the same 'c << 126 matching task is found. << 127 << 128 Use of this feature includes: << 129 - mitigation of some (not all) SMT << 130 - limiting SMT interference to impr << 131 << 132 SCHED_CORE is default disabled. When << 133 which is the likely usage by Linux d << 134 be no measurable impact on performan << 135 << 136 <<
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