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 !PREEMPT_RCU && !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
94 default NEED_TASKS_RCU && (PREEMPTION || PREEMPT_AUTO)
99 depends on RCU_EXPERT
101 default n
103 This option force-enables a task-based RCU implementation
105 user-mode execution as quiescent states. It forces IPIs and
106 context switches on all online CPUs, including idle ones,
111 default n
116 depends on RCU_EXPERT
118 default n
120 This option enables a task-based RCU implementation that uses
121 explicit rcu_read_lock_trace() read-side markers, and allows
122 these readers to appear in the idle loop as well as on the
123 CPU hotplug code paths. It can force IPIs on online CPUs,
129 default n
144 int "Tree-based hierarchical RCU fanout value"
147 depends on TREE_RCU && RCU_EXPERT
148 default 64 if 64BIT
149 default 32 if !64BIT
152 of RCU, allowing RCU to work efficiently on machines with
155 The default value of RCU_FANOUT should be used for production
156 systems, but if you are stress-testing the RCU implementation
157 itself, small RCU_FANOUT values allow you to test large-system
158 code paths on small(er) systems.
161 Take the default if unsure.
164 int "Tree-based hierarchical RCU leaf-level fanout value"
168 depends on TREE_RCU && RCU_EXPERT
169 default 16 if !RCU_STRICT_GRACE_PERIOD
170 default 2 if RCU_STRICT_GRACE_PERIOD
172 This option controls the leaf-level fanout of hierarchical
175 scheduling-clock interrupts for energy-efficiency reasons will
176 want the default because the smaller leaf-level fanout keeps
180 number of cache misses incurred during RCU's grace-period
181 initialization. These systems tend to run CPU-bound, and thus
184 leaf-level fanouts work well. That said, setting leaf-level
186 lock contention on the leaf-level rcu_node structures unless
193 kernel boot parameter to avoid contention on the rcu_node
196 Take the default if unsure.
200 depends on (RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT) || PREEMPT_RT
201 default y if PREEMPT_RT
208 Say Y here if you are working with real-time apps or heavy loads
212 int "Milliseconds to delay boosting after RCU grace-period start"
214 depends on RCU_BOOST
215 default 500
218 a given grace period before priority-boosting preempted RCU
222 Accept the default if unsure.
225 bool "Perform RCU expedited work in a real-time kthread"
226 depends on RCU_BOOST && RCU_EXPERT
227 default !PREEMPT_RT && NR_CPUS <= 32
232 This option is disabled by default on PREEMPT_RT=y kernels which
236 Accept the default if unsure.
239 bool "Offload RCU callback processing from boot-selected CPUs"
240 depends on TREE_RCU
241 depends on RCU_EXPERT || NO_HZ_FULL
242 default n
245 real-time workloads. It can also be used to offload RCU
246 callback invocation to energy-efficient CPUs in battery-powered
249 workloads will incur significant increases in context-switch
256 and where the "x" is "p" for RCU-preempt (PREEMPTION kernels)
257 and "s" for RCU-sched (!PREEMPTION kernels). This option
261 prevents these kthreads from running on the specified CPUs,
264 to run on whatever set of CPUs is desired.
275 bool "Offload RCU callback processing from all CPUs by default"
276 depends on RCU_NOCB_CPU
277 default n
280 by default, in the absence of the rcu_nocbs or nohz_full boot
282 to achieve the effect of offloading all CPUs on boot.
284 Say Y here if you want offload all CPUs by default on boot.
288 bool "Offload RCU callback from real-time kthread"
289 depends on RCU_NOCB_CPU && RCU_BOOST
290 default y if PREEMPT_RT
297 it is your responsibility to ensure that latency-sensitive
298 tasks either run with higher priority or run on some other CPU.
305 depends on RCU_EXPERT && TASKS_TRACE_RCU
306 default PREEMPT_RT || NR_CPUS < 8
314 real-time installations and for battery-powered devices,
315 hence the default chosen above.
318 Say N here if you hate read-side memory barriers.
319 Take the default if you are unsure.
323 depends on RCU_NOCB_CPU
324 default n
334 bool "Turn RCU lazy invocation off by default"
335 depends on RCU_LAZY
336 default n
338 Allows building the kernel with CONFIG_RCU_LAZY=y yet keep it default
340 it back on.
343 bool "RCU callback-batch backup time check"
344 depends on RCU_EXPERT
345 default n
350 thus defeating the 32-callback batching used to amortize the
351 cost of the fine-grained but expensive local_clock() function.
354 jiffy, and overrides the 32-callback batching if this limit
357 Say Y here if you need tighter callback-limit enforcement.