Linux/kernel/rcu/Kconfig

Version: ~ [ linux-6.11.5 ] ~ [ linux-6.10.14 ] ~ [ linux-6.9.12 ] ~ [ linux-6.8.12 ] ~ [ linux-6.7.12 ] ~ [ linux-6.6.58 ] ~ [ linux-6.5.13 ] ~ [ linux-6.4.16 ] ~ [ linux-6.3.13 ] ~ [ linux-6.2.16 ] ~ [ linux-6.1.114 ] ~ [ linux-6.0.19 ] ~ [ linux-5.19.17 ] ~ [ linux-5.18.19 ] ~ [ linux-5.17.15 ] ~ [ linux-5.16.20 ] ~ [ linux-5.15.169 ] ~ [ linux-5.14.21 ] ~ [ linux-5.13.19 ] ~ [ linux-5.12.19 ] ~ [ linux-5.11.22 ] ~ [ linux-5.10.228 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.284 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.322 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.336 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.337 ] ~ [ linux-4.4.302 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.9 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

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1 # SPDX-License-Identifier: GPL-2.0-only << 2 # 1 # 3 # RCU-related configuration options 2 # RCU-related configuration options 4 # 3 # 5 4 6 menu "RCU Subsystem" 5 menu "RCU Subsystem" 7 6 8 config TREE_RCU 7 config TREE_RCU 9 bool 8 bool 10 default y if SMP !! 9 default y if !PREEMPT && SMP 11 # Dynticks-idle tracking << 12 select CONTEXT_TRACKING_IDLE << 13 help 10 help 14 This option selects the RCU implemen 11 This option selects the RCU implementation that is 15 designed for very large SMP system w 12 designed for very large SMP system with hundreds or 16 thousands of CPUs. It also scales d 13 thousands of CPUs. It also scales down nicely to 17 smaller systems. 14 smaller systems. 18 15 19 config PREEMPT_RCU 16 config PREEMPT_RCU 20 bool 17 bool 21 default y if PREEMPTION !! 18 default y if PREEMPT 22 select TREE_RCU << 23 help 19 help 24 This option selects the RCU implemen 20 This option selects the RCU implementation that is 25 designed for very large SMP systems 21 designed for very large SMP systems with hundreds or 26 thousands of CPUs, but for which rea 22 thousands of CPUs, but for which real-time response 27 is also required. It also scales do 23 is also required. It also scales down nicely to 28 smaller systems. 24 smaller systems. 29 25 30 Select this option if you are unsure 26 Select this option if you are unsure. 31 27 32 config TINY_RCU 28 config TINY_RCU 33 bool 29 bool 34 default y if !PREEMPT_RCU && !SMP !! 30 default y if !PREEMPT && !SMP 35 help 31 help 36 This option selects the RCU implemen 32 This option selects the RCU implementation that is 37 designed for UP systems from which r 33 designed for UP systems from which real-time response 38 is not required. This option greatl 34 is not required. This option greatly reduces the 39 memory footprint of RCU. 35 memory footprint of RCU. 40 36 41 config RCU_EXPERT 37 config RCU_EXPERT 42 bool "Make expert-level adjustments to 38 bool "Make expert-level adjustments to RCU configuration" 43 default n 39 default n 44 help 40 help 45 This option needs to be enabled if y 41 This option needs to be enabled if you wish to make 46 expert-level adjustments to RCU conf 42 expert-level adjustments to RCU configuration. By default, 47 no such adjustments can be made, whi 43 no such adjustments can be made, which has the often-beneficial 48 side-effect of preventing "make oldc 44 side-effect of preventing "make oldconfig" from asking you all 49 sorts of detailed questions about ho 45 sorts of detailed questions about how you would like numerous 50 obscure RCU options to be set up. 46 obscure RCU options to be set up. 51 47 52 Say Y if you need to make expert-lev 48 Say Y if you need to make expert-level adjustments to RCU. 53 49 54 Say N if you are unsure. 50 Say N if you are unsure. 55 51 >> 52 config SRCU >> 53 bool >> 54 help >> 55 This option selects the sleepable version of RCU. This version >> 56 permits arbitrary sleeping or blocking within RCU read-side critical >> 57 sections. >> 58 56 config TINY_SRCU 59 config TINY_SRCU 57 bool 60 bool 58 default y if TINY_RCU !! 61 default y if SRCU && TINY_RCU 59 help 62 help 60 This option selects the single-CPU n 63 This option selects the single-CPU non-preemptible version of SRCU. 61 64 62 config TREE_SRCU 65 config TREE_SRCU 63 bool 66 bool 64 default y if !TINY_RCU !! 67 default y if SRCU && !TINY_RCU 65 help 68 help 66 This option selects the full-fledged 69 This option selects the full-fledged version of SRCU. 67 70 68 config NEED_SRCU_NMI_SAFE << 69 def_bool HAVE_NMI && !ARCH_HAS_NMI_SAF << 70 << 71 config TASKS_RCU_GENERIC << 72 def_bool TASKS_RCU || TASKS_RUDE_RCU | << 73 help << 74 This option enables generic infrastr << 75 task-based RCU implementations. Not << 76 << 77 config FORCE_TASKS_RCU << 78 bool "Force selection of TASKS_RCU" << 79 depends on RCU_EXPERT << 80 select TASKS_RCU << 81 default n << 82 help << 83 This option force-enables a task-bas << 84 that uses only voluntary context swi << 85 idle, and user-mode execution as qui << 86 manual selection in most cases. << 87 << 88 config NEED_TASKS_RCU << 89 bool << 90 default n << 91 << 92 config TASKS_RCU 71 config TASKS_RCU 93 bool 72 bool 94 default NEED_TASKS_RCU && (PREEMPTION << 95 select IRQ_WORK << 96 << 97 config FORCE_TASKS_RUDE_RCU << 98 bool "Force selection of Tasks Rude RC << 99 depends on RCU_EXPERT << 100 select TASKS_RUDE_RCU << 101 default n << 102 help << 103 This option force-enables a task-bas << 104 that uses only context switch (inclu << 105 user-mode execution as quiescent sta << 106 context switches on all online CPUs, << 107 so use with caution. Not for manual << 108 << 109 config TASKS_RUDE_RCU << 110 bool << 111 default n << 112 select IRQ_WORK << 113 << 114 config FORCE_TASKS_TRACE_RCU << 115 bool "Force selection of Tasks Trace R << 116 depends on RCU_EXPERT << 117 select TASKS_TRACE_RCU << 118 default n 73 default n >> 74 select SRCU 119 help 75 help 120 This option enables a task-based RCU 76 This option enables a task-based RCU implementation that uses 121 explicit rcu_read_lock_trace() read- !! 77 only voluntary context switch (not preemption!), idle, and 122 these readers to appear in the idle !! 78 user-mode execution as quiescent states. 123 CPU hotplug code paths. It can forc << 124 including idle ones, so use with cau << 125 selection in most cases. << 126 << 127 config TASKS_TRACE_RCU << 128 bool << 129 default n << 130 select IRQ_WORK << 131 79 132 config RCU_STALL_COMMON 80 config RCU_STALL_COMMON 133 def_bool TREE_RCU !! 81 def_bool ( TREE_RCU || PREEMPT_RCU ) 134 help 82 help 135 This option enables RCU CPU stall co 83 This option enables RCU CPU stall code that is common between 136 the TINY and TREE variants of RCU. 84 the TINY and TREE variants of RCU. The purpose is to allow 137 the tiny variants to disable RCU CPU 85 the tiny variants to disable RCU CPU stall warnings, while 138 making these warnings mandatory for 86 making these warnings mandatory for the tree variants. 139 87 140 config RCU_NEED_SEGCBLIST 88 config RCU_NEED_SEGCBLIST 141 def_bool ( TREE_RCU || TREE_SRCU || TA !! 89 def_bool ( TREE_RCU || PREEMPT_RCU || TREE_SRCU ) >> 90 >> 91 config CONTEXT_TRACKING >> 92 bool >> 93 >> 94 config CONTEXT_TRACKING_FORCE >> 95 bool "Force context tracking" >> 96 depends on CONTEXT_TRACKING >> 97 default y if !NO_HZ_FULL >> 98 help >> 99 The major pre-requirement for full dynticks to work is to >> 100 support the context tracking subsystem. But there are also >> 101 other dependencies to provide in order to make the full >> 102 dynticks working. >> 103 >> 104 This option stands for testing when an arch implements the >> 105 context tracking backend but doesn't yet fullfill all the >> 106 requirements to make the full dynticks feature working. >> 107 Without the full dynticks, there is no way to test the support >> 108 for context tracking and the subsystems that rely on it: RCU >> 109 userspace extended quiescent state and tickless cputime >> 110 accounting. This option copes with the absence of the full >> 111 dynticks subsystem by forcing the context tracking on all >> 112 CPUs in the system. >> 113 >> 114 Say Y only if you're working on the development of an >> 115 architecture backend for the context tracking. >> 116 >> 117 Say N otherwise, this option brings an overhead that you >> 118 don't want in production. >> 119 142 120 143 config RCU_FANOUT 121 config RCU_FANOUT 144 int "Tree-based hierarchical RCU fanou 122 int "Tree-based hierarchical RCU fanout value" 145 range 2 64 if 64BIT 123 range 2 64 if 64BIT 146 range 2 32 if !64BIT 124 range 2 32 if !64BIT 147 depends on TREE_RCU && RCU_EXPERT !! 125 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT 148 default 64 if 64BIT 126 default 64 if 64BIT 149 default 32 if !64BIT 127 default 32 if !64BIT 150 help 128 help 151 This option controls the fanout of h 129 This option controls the fanout of hierarchical implementations 152 of RCU, allowing RCU to work efficie 130 of RCU, allowing RCU to work efficiently on machines with 153 large numbers of CPUs. This value m 131 large numbers of CPUs. This value must be at least the fourth 154 root of NR_CPUS, which allows NR_CPU 132 root of NR_CPUS, which allows NR_CPUS to be insanely large. 155 The default value of RCU_FANOUT shou 133 The default value of RCU_FANOUT should be used for production 156 systems, but if you are stress-testi 134 systems, but if you are stress-testing the RCU implementation 157 itself, small RCU_FANOUT values allo 135 itself, small RCU_FANOUT values allow you to test large-system 158 code paths on small(er) systems. 136 code paths on small(er) systems. 159 137 160 Select a specific number if testing 138 Select a specific number if testing RCU itself. 161 Take the default if unsure. 139 Take the default if unsure. 162 140 163 config RCU_FANOUT_LEAF 141 config RCU_FANOUT_LEAF 164 int "Tree-based hierarchical RCU leaf- 142 int "Tree-based hierarchical RCU leaf-level fanout value" 165 range 2 64 if 64BIT && !RCU_STRICT_GRA !! 143 range 2 64 if 64BIT 166 range 2 32 if !64BIT && !RCU_STRICT_GR !! 144 range 2 32 if !64BIT 167 range 2 3 if RCU_STRICT_GRACE_PERIOD !! 145 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT 168 depends on TREE_RCU && RCU_EXPERT !! 146 default 16 169 default 16 if !RCU_STRICT_GRACE_PERIOD << 170 default 2 if RCU_STRICT_GRACE_PERIOD << 171 help 147 help 172 This option controls the leaf-level 148 This option controls the leaf-level fanout of hierarchical 173 implementations of RCU, and allows t 149 implementations of RCU, and allows trading off cache misses 174 against lock contention. Systems th 150 against lock contention. Systems that synchronize their 175 scheduling-clock interrupts for ener 151 scheduling-clock interrupts for energy-efficiency reasons will 176 want the default because the smaller 152 want the default because the smaller leaf-level fanout keeps 177 lock contention levels acceptably lo 153 lock contention levels acceptably low. Very large systems 178 (hundreds or thousands of CPUs) will 154 (hundreds or thousands of CPUs) will instead want to set this 179 value to the maximum value possible 155 value to the maximum value possible in order to reduce the 180 number of cache misses incurred duri 156 number of cache misses incurred during RCU's grace-period 181 initialization. These systems tend 157 initialization. These systems tend to run CPU-bound, and thus 182 are not helped by synchronized inter 158 are not helped by synchronized interrupts, and thus tend to 183 skew them, which reduces lock conten 159 skew them, which reduces lock contention enough that large 184 leaf-level fanouts work well. That 160 leaf-level fanouts work well. That said, setting leaf-level 185 fanout to a large number will likely 161 fanout to a large number will likely cause problematic 186 lock contention on the leaf-level rc 162 lock contention on the leaf-level rcu_node structures unless 187 you boot with the skew_tick kernel p 163 you boot with the skew_tick kernel parameter. 188 164 189 Select a specific number if testing 165 Select a specific number if testing RCU itself. 190 166 191 Select the maximum permissible value 167 Select the maximum permissible value for large systems, but 192 please understand that you may also 168 please understand that you may also need to set the skew_tick 193 kernel boot parameter to avoid conte 169 kernel boot parameter to avoid contention on the rcu_node 194 structure's locks. 170 structure's locks. 195 171 196 Take the default if unsure. 172 Take the default if unsure. 197 173 >> 174 config RCU_FAST_NO_HZ >> 175 bool "Accelerate last non-dyntick-idle CPU's grace periods" >> 176 depends on NO_HZ_COMMON && SMP && RCU_EXPERT >> 177 default n >> 178 help >> 179 This option permits CPUs to enter dynticks-idle state even if >> 180 they have RCU callbacks queued, and prevents RCU from waking >> 181 these CPUs up more than roughly once every four jiffies (by >> 182 default, you can adjust this using the rcutree.rcu_idle_gp_delay >> 183 parameter), thus improving energy efficiency. On the other >> 184 hand, this option increases the duration of RCU grace periods, >> 185 for example, slowing down synchronize_rcu(). >> 186 >> 187 Say Y if energy efficiency is critically important, and you >> 188 don't care about increased grace-period durations. >> 189 >> 190 Say N if you are unsure. >> 191 198 config RCU_BOOST 192 config RCU_BOOST 199 bool "Enable RCU priority boosting" 193 bool "Enable RCU priority boosting" 200 depends on (RT_MUTEXES && PREEMPT_RCU !! 194 depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT 201 default y if PREEMPT_RT !! 195 default n 202 help 196 help 203 This option boosts the priority of p 197 This option boosts the priority of preempted RCU readers that 204 block the current preemptible RCU gr 198 block the current preemptible RCU grace period for too long. 205 This option also prevents heavy load 199 This option also prevents heavy loads from blocking RCU 206 callback invocation. !! 200 callback invocation for all flavors of RCU. 207 201 208 Say Y here if you are working with r 202 Say Y here if you are working with real-time apps or heavy loads 209 Say N here if you are unsure. 203 Say N here if you are unsure. 210 204 211 config RCU_BOOST_DELAY 205 config RCU_BOOST_DELAY 212 int "Milliseconds to delay boosting af 206 int "Milliseconds to delay boosting after RCU grace-period start" 213 range 0 3000 207 range 0 3000 214 depends on RCU_BOOST 208 depends on RCU_BOOST 215 default 500 209 default 500 216 help 210 help 217 This option specifies the time to wa 211 This option specifies the time to wait after the beginning of 218 a given grace period before priority 212 a given grace period before priority-boosting preempted RCU 219 readers blocking that grace period. 213 readers blocking that grace period. Note that any RCU reader 220 blocking an expedited RCU grace peri 214 blocking an expedited RCU grace period is boosted immediately. 221 215 222 Accept the default if unsure. 216 Accept the default if unsure. 223 217 224 config RCU_EXP_KTHREAD << 225 bool "Perform RCU expedited work in a << 226 depends on RCU_BOOST && RCU_EXPERT << 227 default !PREEMPT_RT && NR_CPUS <= 32 << 228 help << 229 Use this option to further reduce th << 230 grace periods at the expense of bein << 231 << 232 This option is disabled by default o << 233 disable expedited grace periods afte << 234 setting rcupdate.rcu_normal_after_bo << 235 << 236 Accept the default if unsure. << 237 << 238 config RCU_NOCB_CPU 218 config RCU_NOCB_CPU 239 bool "Offload RCU callback processing 219 bool "Offload RCU callback processing from boot-selected CPUs" 240 depends on TREE_RCU !! 220 depends on TREE_RCU || PREEMPT_RCU 241 depends on RCU_EXPERT || NO_HZ_FULL 221 depends on RCU_EXPERT || NO_HZ_FULL 242 default n 222 default n 243 help 223 help 244 Use this option to reduce OS jitter 224 Use this option to reduce OS jitter for aggressive HPC or 245 real-time workloads. It can also be 225 real-time workloads. It can also be used to offload RCU 246 callback invocation to energy-effici 226 callback invocation to energy-efficient CPUs in battery-powered 247 asymmetric multiprocessors. The pri !! 227 asymmetric multiprocessors. 248 is that the overhead of call_rcu() i << 249 workloads will incur significant inc << 250 rates. << 251 << 252 This option offloads callback invoca << 253 specified at boot time by the rcu_no << 254 such CPU, a kthread ("rcuox/N") will << 255 callbacks, where the "N" is the CPU << 256 the "x" is "p" for RCU-preempt (PREE << 257 RCU-sched (!PREEMPTION kernels). No << 258 from running on the specified CPUs, << 259 preempted between each callback, and << 260 be used to force the kthreads to run << 261 desired. << 262 228 263 Say Y here if you need reduced OS ji !! 229 This option offloads callback invocation from the set of 264 Say N here if you are unsure. !! 230 CPUs specified at boot time by the rcu_nocbs parameter. 265 !! 231 For each such CPU, a kthread ("rcuox/N") will be created to 266 config RCU_NOCB_CPU_DEFAULT_ALL !! 232 invoke callbacks, where the "N" is the CPU being offloaded, 267 bool "Offload RCU callback processing !! 233 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and 268 depends on RCU_NOCB_CPU !! 234 "s" for RCU-sched. Nothing prevents this kthread from running 269 default n !! 235 on the specified CPUs, but (1) the kthreads may be preempted 270 help !! 236 between each callback, and (2) affinity or cgroups can be used 271 Use this option to offload callback !! 237 to force the kthreads to run on whatever set of CPUs is desired. 272 by default, in the absence of the rc << 273 parameter. This also avoids the need << 274 to achieve the effect of offloading << 275 << 276 Say Y here if you want offload all C << 277 Say N here if you are unsure. << 278 << 279 config RCU_NOCB_CPU_CB_BOOST << 280 bool "Offload RCU callback from real-t << 281 depends on RCU_NOCB_CPU && RCU_BOOST << 282 default y if PREEMPT_RT << 283 help << 284 Use this option to invoke offloaded << 285 to avoid starvation by heavy SCHED_O << 286 Of course, running as SCHED_FIFO dur << 287 cause the rcuo[ps] kthreads to monop << 288 of milliseconds or more. Therefore, << 289 it is your responsibility to ensure << 290 tasks either run with higher priorit << 291 << 292 Say Y here if you want to set RT pri << 293 Say N here if you are building a !PR << 294 << 295 config TASKS_TRACE_RCU_READ_MB << 296 bool "Tasks Trace RCU readers use memo << 297 depends on RCU_EXPERT && TASKS_TRACE_R << 298 default PREEMPT_RT || NR_CPUS < 8 << 299 help << 300 Use this option to further reduce th << 301 to CPUs executing in userspace or id << 302 RCU grace periods. Given that a rea << 303 the rcupdate.rcu_task_ipi_delay kern << 304 eliminates such IPIs for many worklo << 305 of this Kconfig option is important << 306 real-time installations and for batt << 307 hence the default chosen above. << 308 << 309 Say Y here if you hate IPIs. << 310 Say N here if you hate read-side mem << 311 Take the default if you are unsure. << 312 << 313 config RCU_LAZY << 314 bool "RCU callback lazy invocation fun << 315 depends on RCU_NOCB_CPU << 316 default n << 317 help << 318 To save power, batch RCU callbacks a << 319 pressure, or callback list growing t << 320 << 321 Requires rcu_nocbs=all to be set. << 322 << 323 Use rcutree.enable_rcu_lazy=0 to tur << 324 << 325 config RCU_LAZY_DEFAULT_OFF << 326 bool "Turn RCU lazy invocation off by << 327 depends on RCU_LAZY << 328 default n << 329 help << 330 Allows building the kernel with CONF << 331 off. Boot time param rcutree.enable_ << 332 it back on. << 333 << 334 config RCU_DOUBLE_CHECK_CB_TIME << 335 bool "RCU callback-batch backup time c << 336 depends on RCU_EXPERT << 337 default n << 338 help << 339 Use this option to provide more prec << 340 rcutree.rcu_resched_ns module parame << 341 a single RCU callback might run for << 342 thus defeating the 32-callback batch << 343 cost of the fine-grained but expensi << 344 << 345 This option rounds rcutree.rcu_resch << 346 jiffy, and overrides the 32-callback << 347 is exceeded. << 348 238 349 Say Y here if you need tighter callb !! 239 Say Y here if you want to help to debug reduced OS jitter. 350 Say N here if you are unsure. 240 Say N here if you are unsure. 351 241 352 endmenu # "RCU Subsystem" 242 endmenu # "RCU Subsystem"

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Linux/kernel/rcu/Kconfig

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Differences between /kernel/rcu/Kconfig (Version linux-6.11.5) and /kernel/rcu/Kconfig (Version linux-4.13.16)

TOMOYO Linux Cross Reference Linux/kernel/rcu/Kconfig

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Differences between /kernel/rcu/Kconfig (Version linux-6.11.5) and /kernel/rcu/Kconfig (Version linux-4.13.16)

TOMOYO Linux Cross Reference
Linux/kernel/rcu/Kconfig