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Ingo Molnarcc19ca82005-06-25 14:57:36 -07001
Ingo Molnarf8cbd992005-06-25 14:57:39 -07002choice
3 prompt "Preemption Model"
4 default PREEMPT_NONE
5
6config PREEMPT_NONE
7 bool "No Forced Preemption (Server)"
Ingo Molnarcc19ca82005-06-25 14:57:36 -07008 help
Ingo Molnarf8cbd992005-06-25 14:57:39 -07009 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,
David Sterba3dde6ad2007-05-09 07:12:20 +020026 at the cost of slightly lower throughput.
Ingo Molnarf8cbd992005-06-25 14:57:39 -070027
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 Molnarcc19ca82005-06-25 14:57:36 -070032 under load.
33
Ingo Molnarf8cbd992005-06-25 14:57:39 -070034 Select this if you are building a kernel for a desktop system.
35
36config 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 Sterba3dde6ad2007-05-09 07:12:20 +020046 system is under load, at the cost of slightly lower throughput
Ingo Molnarf8cbd992005-06-25 14:57:39 -070047 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
53endchoice
Ingo Molnarcc19ca82005-06-25 14:57:36 -070054
Paul E. McKenney21bbb392008-03-10 11:43:57 -070055config 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
Paul E. McKenneye260be62008-01-25 21:08:24 +010069config RCU_TRACE
70 bool "Enable tracing for RCU - currently stats in debugfs"
Paul E. McKenney21bbb392008-03-10 11:43:57 -070071 depends on PREEMPT_RCU
Paul E. McKenneye260be62008-01-25 21:08:24 +010072 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.