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 (PREEMPT || PREEMPT_RT || PREEMPT_DYNAMIC)
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.
70 depends on !TINY_SRCU
71 depends on RCU_EXPERT
72 depends on ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
74 default n
78 and srcu_read_unlock_nmisafe() on architectures (like x86)
88 task-based RCU implementations. Not for manual selection.
92 depends on RCU_EXPERT
94 default n
96 This option force-enables a task-based RCU implementation
98 idle, and user-mode execution as quiescent states. Not for
103 default n
107 default NEED_TASKS_RCU && PREEMPTION
112 depends on RCU_EXPERT
114 default n
116 This option force-enables a task-based RCU implementation
118 user-mode execution as quiescent states. It forces IPIs and
119 context switches on all online CPUs, including idle ones,
124 default n
129 depends on RCU_EXPERT
131 default n
133 This option enables a task-based RCU implementation that uses
134 explicit rcu_read_lock_trace() read-side markers, and allows
135 these readers to appear in the idle loop as well as on the
136 CPU hotplug code paths. It can force IPIs on online CPUs,
142 default n
157 int "Tree-based hierarchical RCU fanout value"
160 depends on TREE_RCU && RCU_EXPERT
161 default 64 if 64BIT
162 default 32 if !64BIT
165 of RCU, allowing RCU to work efficiently on machines with
168 The default value of RCU_FANOUT should be used for production
169 systems, but if you are stress-testing the RCU implementation
170 itself, small RCU_FANOUT values allow you to test large-system
171 code paths on small(er) systems.
174 Take the default if unsure.
177 int "Tree-based hierarchical RCU leaf-level fanout value"
181 depends on TREE_RCU && RCU_EXPERT
182 default 16 if !RCU_STRICT_GRACE_PERIOD
183 default 2 if RCU_STRICT_GRACE_PERIOD
185 This option controls the leaf-level fanout of hierarchical
188 scheduling-clock interrupts for energy-efficiency reasons will
189 want the default because the smaller leaf-level fanout keeps
193 number of cache misses incurred during RCU's grace-period
194 initialization. These systems tend to run CPU-bound, and thus
197 leaf-level fanouts work well. That said, setting leaf-level
199 lock contention on the leaf-level rcu_node structures unless
206 kernel boot parameter to avoid contention on the rcu_node
209 Take the default if unsure.
213 depends on (RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT) || PREEMPT_RT
214 default y if PREEMPT_RT
221 Say Y here if you are working with real-time apps or heavy loads
225 int "Milliseconds to delay boosting after RCU grace-period start"
227 depends on RCU_BOOST
228 default 500
231 a given grace period before priority-boosting preempted RCU
235 Accept the default if unsure.
238 bool "Perform RCU expedited work in a real-time kthread"
239 depends on RCU_BOOST && RCU_EXPERT
240 default !PREEMPT_RT && NR_CPUS <= 32
245 This option is disabled by default on PREEMPT_RT=y kernels which
249 Accept the default if unsure.
252 bool "Offload RCU callback processing from boot-selected CPUs"
253 depends on TREE_RCU
254 depends on RCU_EXPERT || NO_HZ_FULL
255 default n
258 real-time workloads. It can also be used to offload RCU
259 callback invocation to energy-efficient CPUs in battery-powered
262 workloads will incur significant increases in context-switch
269 and where the "x" is "p" for RCU-preempt (PREEMPTION kernels)
270 and "s" for RCU-sched (!PREEMPTION kernels). This option
274 prevents these kthreads from running on the specified CPUs,
277 to run on whatever set of CPUs is desired.
288 bool "Offload RCU callback processing from all CPUs by default"
289 depends on RCU_NOCB_CPU
290 default n
293 by default, in the absence of the rcu_nocbs or nohz_full boot
295 to achieve the effect of offloading all CPUs on boot.
297 Say Y here if you want offload all CPUs by default on boot.
301 bool "Offload RCU callback from real-time kthread"
302 depends on RCU_NOCB_CPU && RCU_BOOST
303 default y if PREEMPT_RT
310 it is your responsibility to ensure that latency-sensitive
311 tasks either run with higher priority or run on some other CPU.
318 depends on RCU_EXPERT && TASKS_TRACE_RCU
319 default PREEMPT_RT || NR_CPUS < 8
327 real-time installations and for battery-powered devices,
328 hence the default chosen above.
331 Say N here if you hate read-side memory barriers.
332 Take the default if you are unsure.
336 depends on RCU_NOCB_CPU
337 default n
345 These delays happen only on rcu_nocbs CPUs, that is, CPUs
348 Use the rcutree.enable_rcu_lazy=0 kernel-boot parameter to
352 bool "Turn RCU lazy invocation off by default"
353 depends on RCU_LAZY
354 default n
357 to boot with these energy-efficiency delays disabled. Use the
358 rcutree.enable_rcu_lazy=0 kernel-boot parameter to override
359 the this option at boot time, thus re-enabling these delays.
362 bool "RCU callback-batch backup time check"
363 depends on RCU_EXPERT
364 default n
369 thus defeating the 32-callback batching used to amortize the
370 cost of the fine-grained but expensive local_clock() function.
373 jiffy, and overrides the 32-callback batching if this limit
376 Say Y here if you need tighter callback-limit enforcement.