kernel/Kconfig.preempt

   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