Lines Matching +full:default +full:- +full:on
1 # SPDX-License-Identifier: GPL-2.0-only
3 # RCU-related configuration options
10 default y if SMP
11 # Dynticks-idle tracking
21 default y if PREEMPTION
26 thousands of CPUs, but for which real-time response
34 default y if !PREEMPTION && !SMP
37 designed for UP systems from which real-time response
42 bool "Make expert-level adjustments to RCU configuration"
43 default n
46 expert-level adjustments to RCU configuration. By default,
47 no such adjustments can be made, which has the often-beneficial
48 side-effect of preventing "make oldconfig" from asking you all
52 Say Y if you need to make expert-level adjustments to RCU.
58 default y if TINY_RCU
60 This option selects the single-CPU non-preemptible version of SRCU.
64 default y if !TINY_RCU
66 This option selects the full-fledged version of SRCU.
75 task-based RCU implementations. Not for manual selection.
79 depends on RCU_EXPERT
81 default n
83 This option force-enables a task-based RCU implementation
85 idle, and user-mode execution as quiescent states. Not for
90 default n
95 depends on RCU_EXPERT
97 default n
99 This option force-enables a task-based RCU implementation
101 user-mode execution as quiescent states. It forces IPIs and
102 context switches on all online CPUs, including idle ones,
107 default n
112 depends on RCU_EXPERT
114 default n
116 This option enables a task-based RCU implementation that uses
117 explicit rcu_read_lock_trace() read-side markers, and allows
118 these readers to appear in the idle loop as well as on the
119 CPU hotplug code paths. It can force IPIs on online CPUs,
125 default n
140 int "Tree-based hierarchical RCU fanout value"
143 depends on TREE_RCU && RCU_EXPERT
144 default 64 if 64BIT
145 default 32 if !64BIT
148 of RCU, allowing RCU to work efficiently on machines with
151 The default value of RCU_FANOUT should be used for production
152 systems, but if you are stress-testing the RCU implementation
153 itself, small RCU_FANOUT values allow you to test large-system
154 code paths on small(er) systems.
157 Take the default if unsure.
160 int "Tree-based hierarchical RCU leaf-level fanout value"
164 depends on TREE_RCU && RCU_EXPERT
165 default 16 if !RCU_STRICT_GRACE_PERIOD
166 default 2 if RCU_STRICT_GRACE_PERIOD
168 This option controls the leaf-level fanout of hierarchical
171 scheduling-clock interrupts for energy-efficiency reasons will
172 want the default because the smaller leaf-level fanout keeps
176 number of cache misses incurred during RCU's grace-period
177 initialization. These systems tend to run CPU-bound, and thus
180 leaf-level fanouts work well. That said, setting leaf-level
182 lock contention on the leaf-level rcu_node structures unless
189 kernel boot parameter to avoid contention on the rcu_node
192 Take the default if unsure.
196 depends on (RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT) || PREEMPT_RT
197 default y if PREEMPT_RT
204 Say Y here if you are working with real-time apps or heavy loads
208 int "Milliseconds to delay boosting after RCU grace-period start"
210 depends on RCU_BOOST
211 default 500
214 a given grace period before priority-boosting preempted RCU
218 Accept the default if unsure.
221 bool "Perform RCU expedited work in a real-time kthread"
222 depends on RCU_BOOST && RCU_EXPERT
223 default !PREEMPT_RT && NR_CPUS <= 32
228 This option is disabled by default on PREEMPT_RT=y kernels which
232 Accept the default if unsure.
235 bool "Offload RCU callback processing from boot-selected CPUs"
236 depends on TREE_RCU
237 depends on RCU_EXPERT || NO_HZ_FULL
238 default n
241 real-time workloads. It can also be used to offload RCU
242 callback invocation to energy-efficient CPUs in battery-powered
245 workloads will incur significant increases in context-switch
252 the "x" is "p" for RCU-preempt (PREEMPTION kernels) and "s" for
253 RCU-sched (!PREEMPTION kernels). Nothing prevents this kthread
254 from running on the specified CPUs, but (1) the kthreads may be
256 be used to force the kthreads to run on whatever set of CPUs is
263 bool "Offload RCU callback processing from all CPUs by default"
264 depends on RCU_NOCB_CPU
265 default n
268 by default, in the absence of the rcu_nocbs or nohz_full boot
270 to achieve the effect of offloading all CPUs on boot.
272 Say Y here if you want offload all CPUs by default on boot.
276 bool "Offload RCU callback from real-time kthread"
277 depends on RCU_NOCB_CPU && RCU_BOOST
278 default y if PREEMPT_RT
285 it is your responsibility to ensure that latency-sensitive
286 tasks either run with higher priority or run on some other CPU.
293 depends on RCU_EXPERT && TASKS_TRACE_RCU
294 default PREEMPT_RT || NR_CPUS < 8
302 real-time installations and for battery-powered devices,
303 hence the default chosen above.
306 Say N here if you hate read-side memory barriers.
307 Take the default if you are unsure.
311 depends on RCU_NOCB_CPU
312 default n
318 bool "RCU callback-batch backup time check"
319 depends on RCU_EXPERT
320 default n
325 thus defeating the 32-callback batching used to amortize the
326 cost of the fine-grained but expensive local_clock() function.
329 jiffy, and overrides the 32-callback batching if this limit
332 Say Y here if you need tighter callback-limit enforcement.