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本帖最后由 瀚海书香 于 2012-04-10 12:36 编辑
回复 1# xparmenides
说白了就是允许抢占的时机点的不同。
PREEMPT_NONE 禁止优先级抢占
PREEMPT_VOLUNTARY 增加自愿抢占的时机，但是禁止内核态抢占
PREEMPT 允许内核态抢占
6config PREEMPT_NONE
7 bool "No Forced Preemption (Server)"
8 help
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
19config 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,
26 at the cost of slightly lower throughput.
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
32 under load.
33
34 Select this if you are building a kernel for a desktop system.
35
36config PREEMPT
37 bool "Preemptible Kernel (Low-Latency Desktop)"
38 select PREEMPT_COUNT
39 help
40 This option reduces the latency of the kernel by making
41 all kernel code (that is not executing in a critical section)
42 preemptible. This allows reaction to interactive events by
43 permitting a low priority process to be preempted involuntarily
44 even if it is in kernel mode executing a system call and would
45 otherwise not be about to reach a natural preemption point.
46 This allows applications to run more 'smoothly' even when the
47 system is under load, at the cost of slightly lower throughput
48 and a slight runtime overhead to kernel code.
49
50 Select this if you are building a kernel for a desktop or
51 embedded system with latency requirements in the milliseconds
52 range.
53
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发表于 2012-04-09 15:30
发表于 2012-04-10 11:59
