1# SPDX-License-Identifier: GPL-2.0-only 2 3choice 4 prompt "Preemption Model" 5 default PREEMPT_NONE 6 7config 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 20config 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 38config PREEMPT_LL 39 bool "Preemptible Kernel (Low-Latency Desktop)" 40 depends on !ARCH_NO_PREEMPT 41 select PREEMPT 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 58config PREEMPT_RT 59 bool "Fully Preemptible Kernel (Real-Time)" 60 depends on EXPERT && ARCH_SUPPORTS_RT 61 select PREEMPT 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 75endchoice 76 77config PREEMPT_COUNT 78 bool 79 80config PREEMPT 81 bool 82 select PREEMPT_COUNT 83