1cc19ca86SIngo Molnar 2f8cbd99bSIngo Molnarchoice 3f8cbd99bSIngo Molnar prompt "Preemption Model" 4f8cbd99bSIngo Molnar default PREEMPT_NONE 5f8cbd99bSIngo Molnar 6f8cbd99bSIngo Molnarconfig PREEMPT_NONE 7f8cbd99bSIngo Molnar bool "No Forced Preemption (Server)" 8cc19ca86SIngo Molnar help 9f8cbd99bSIngo Molnar This is the traditional Linux preemption model, geared towards 10f8cbd99bSIngo Molnar throughput. It will still provide good latencies most of the 11f8cbd99bSIngo Molnar time, but there are no guarantees and occasional longer delays 12f8cbd99bSIngo Molnar are possible. 13f8cbd99bSIngo Molnar 14f8cbd99bSIngo Molnar Select this option if you are building a kernel for a server or 15f8cbd99bSIngo Molnar scientific/computation system, or if you want to maximize the 16f8cbd99bSIngo Molnar raw processing power of the kernel, irrespective of scheduling 17f8cbd99bSIngo Molnar latencies. 18f8cbd99bSIngo Molnar 19f8cbd99bSIngo Molnarconfig PREEMPT_VOLUNTARY 20f8cbd99bSIngo Molnar bool "Voluntary Kernel Preemption (Desktop)" 21f8cbd99bSIngo Molnar help 22f8cbd99bSIngo Molnar This option reduces the latency of the kernel by adding more 23f8cbd99bSIngo Molnar "explicit preemption points" to the kernel code. These new 24f8cbd99bSIngo Molnar preemption points have been selected to reduce the maximum 25f8cbd99bSIngo Molnar latency of rescheduling, providing faster application reactions, 263dde6ad8SDavid Sterba at the cost of slightly lower throughput. 27f8cbd99bSIngo Molnar 28f8cbd99bSIngo Molnar This allows reaction to interactive events by allowing a 29f8cbd99bSIngo Molnar low priority process to voluntarily preempt itself even if it 30f8cbd99bSIngo Molnar is in kernel mode executing a system call. This allows 31f8cbd99bSIngo Molnar applications to run more 'smoothly' even when the system is 32cc19ca86SIngo Molnar under load. 33cc19ca86SIngo Molnar 34f8cbd99bSIngo Molnar Select this if you are building a kernel for a desktop system. 35f8cbd99bSIngo Molnar 36f8cbd99bSIngo Molnarconfig PREEMPT 37f8cbd99bSIngo Molnar bool "Preemptible Kernel (Low-Latency Desktop)" 38bdd4e85dSFrederic Weisbecker select PREEMPT_COUNT 39*e335e3ebSRaghavendra K T select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK 40f8cbd99bSIngo Molnar help 41f8cbd99bSIngo Molnar This option reduces the latency of the kernel by making 42f8cbd99bSIngo Molnar all kernel code (that is not executing in a critical section) 43f8cbd99bSIngo Molnar preemptible. This allows reaction to interactive events by 44f8cbd99bSIngo Molnar permitting a low priority process to be preempted involuntarily 45f8cbd99bSIngo Molnar even if it is in kernel mode executing a system call and would 46f8cbd99bSIngo Molnar otherwise not be about to reach a natural preemption point. 47f8cbd99bSIngo Molnar This allows applications to run more 'smoothly' even when the 483dde6ad8SDavid Sterba system is under load, at the cost of slightly lower throughput 49f8cbd99bSIngo Molnar and a slight runtime overhead to kernel code. 50f8cbd99bSIngo Molnar 51f8cbd99bSIngo Molnar Select this if you are building a kernel for a desktop or 52f8cbd99bSIngo Molnar embedded system with latency requirements in the milliseconds 53f8cbd99bSIngo Molnar range. 54f8cbd99bSIngo Molnar 55f8cbd99bSIngo Molnarendchoice 56cc19ca86SIngo Molnar 57bdd4e85dSFrederic Weisbeckerconfig PREEMPT_COUNT 58bdd4e85dSFrederic Weisbecker bool