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2 | choice |
3 | prompt "Preemption Model" | |
4 | default PREEMPT_NONE | |
5 | ||
6 | config 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 | ||
19 | config PREEMPT_VOLUNTARY | |
20 | bool "Voluntary Kernel Preemption (Desktop)" | |
cc19ca86 | 21 | help |
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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, | |
3dde6ad8 | 26 | at the cost of slightly lower throughput. |
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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 | |
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32 | under load. |
33 | ||
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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 | |
3dde6ad8 | 46 | system is under load, at the cost of slightly lower throughput |
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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 | |
cc19ca86 | 54 | |
21bbb39c PM |
55 | config PREEMPT_RCU |
56 | bool "Preemptible RCU" | |
57 | depends on PREEMPT | |
58 | default n | |
59 | help | |
60 | This option reduces the latency of the kernel by making certain | |
61 | RCU sections preemptible. Normally RCU code is non-preemptible, if | |
62 | this option is selected then read-only RCU sections become | |
63 | preemptible. This helps latency, but may expose bugs due to | |
64 | now-naive assumptions about each RCU read-side critical section | |
65 | remaining on a given CPU through its execution. | |
66 | ||
67 | Say N if you are unsure. | |
68 | ||
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69 | config RCU_TRACE |
70 | bool "Enable tracing for RCU - currently stats in debugfs" | |
21bbb39c | 71 | depends on PREEMPT_RCU |
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72 | select DEBUG_FS |
73 | default y | |
74 | help | |
75 | This option provides tracing in RCU which presents stats | |
76 | in debugfs for debugging RCU implementation. | |
77 | ||
78 | Say Y here if you want to enable RCU tracing | |
79 | Say N if you are unsure. |