| Ingo Molnar | cc19ca8 | 2005-06-25 14:57:36 -0700 | [diff] [blame] | 1 | |
| Ingo Molnar | f8cbd99 | 2005-06-25 14:57:39 -0700 | [diff] [blame] | 2 | choice |
| 3 | prompt "Preemption Model" |
| 4 | default PREEMPT_NONE |
| 5 | |
| 6 | config PREEMPT_NONE |
| 7 | bool "No Forced Preemption (Server)" |
| Ingo Molnar | cc19ca8 | 2005-06-25 14:57:36 -0700 | [diff] [blame] | 8 | help |
| Ingo Molnar | f8cbd99 | 2005-06-25 14:57:39 -0700 | [diff] [blame] | 9 | This is the traditional Linux preemption model, geared towards |
| 10 | throughput. It will still provide good latencies most of the |
| 11 | time, but there are no guarantees and occasional longer delays |
| 12 | are possible. |
| 13 | |
| 14 | Select this option if you are building a kernel for a server or |
| 15 | scientific/computation system, or if you want to maximize the |
| 16 | raw processing power of the kernel, irrespective of scheduling |
| 17 | latencies. |
| 18 | |
| 19 | config PREEMPT_VOLUNTARY |
| 20 | bool "Voluntary Kernel Preemption (Desktop)" |
| 21 | help |
| 22 | This option reduces the latency of the kernel by adding more |
| 23 | "explicit preemption points" to the kernel code. These new |
| 24 | preemption points have been selected to reduce the maximum |
| 25 | latency of rescheduling, providing faster application reactions, |
| David Sterba | 3dde6ad | 2007-05-09 07:12:20 +0200 | [diff] [blame^] | 26 | at the cost of slightly lower throughput. |
| Ingo Molnar | f8cbd99 | 2005-06-25 14:57:39 -0700 | [diff] [blame] | 27 | |
| 28 | This allows reaction to interactive events by allowing a |
| 29 | low priority process to voluntarily preempt itself even if it |
| 30 | is in kernel mode executing a system call. This allows |
| 31 | applications to run more 'smoothly' even when the system is |
| Ingo Molnar | cc19ca8 | 2005-06-25 14:57:36 -0700 | [diff] [blame] | 32 | under load. |
| 33 | |
| Ingo Molnar | f8cbd99 | 2005-06-25 14:57:39 -0700 | [diff] [blame] | 34 | Select this if you are building a kernel for a desktop system. |
| 35 | |
| 36 | config PREEMPT |
| 37 | bool "Preemptible Kernel (Low-Latency Desktop)" |
| 38 | help |
| 39 | This option reduces the latency of the kernel by making |
| 40 | all kernel code (that is not executing in a critical section) |
| 41 | preemptible. This allows reaction to interactive events by |
| 42 | permitting a low priority process to be preempted involuntarily |
| 43 | even if it is in kernel mode executing a system call and would |
| 44 | otherwise not be about to reach a natural preemption point. |
| 45 | This allows applications to run more 'smoothly' even when the |
| David Sterba | 3dde6ad | 2007-05-09 07:12:20 +0200 | [diff] [blame^] | 46 | system is under load, at the cost of slightly lower throughput |
| Ingo Molnar | f8cbd99 | 2005-06-25 14:57:39 -0700 | [diff] [blame] | 47 | and a slight runtime overhead to kernel code. |
| 48 | |
| 49 | Select this if you are building a kernel for a desktop or |
| 50 | embedded system with latency requirements in the milliseconds |
| 51 | range. |
| 52 | |
| 53 | endchoice |
| Ingo Molnar | cc19ca8 | 2005-06-25 14:57:36 -0700 | [diff] [blame] | 54 | |
| 55 | config PREEMPT_BKL |
| 56 | bool "Preempt The Big Kernel Lock" |
| Ingo Molnar | f704f56 | 2005-06-25 14:57:38 -0700 | [diff] [blame] | 57 | depends on SMP || PREEMPT |
| Ingo Molnar | cc19ca8 | 2005-06-25 14:57:36 -0700 | [diff] [blame] | 58 | default y |
| 59 | help |
| 60 | This option reduces the latency of the kernel by making the |
| 61 | big kernel lock preemptible. |
| 62 | |
| 63 | Say Y here if you are building a kernel for a desktop system. |
| 64 | Say N if you are unsure. |
| 65 | |