diff options
Diffstat (limited to 'kernel/rcu/Kconfig')
| -rw-r--r-- | kernel/rcu/Kconfig | 71 |
1 files changed, 51 insertions, 20 deletions
diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig index e7d2dd267593..4d9b21f69eaa 100644 --- a/kernel/rcu/Kconfig +++ b/kernel/rcu/Kconfig @@ -18,7 +18,7 @@ config TREE_RCU config PREEMPT_RCU bool - default y if PREEMPTION + default y if (PREEMPT || PREEMPT_RT || PREEMPT_DYNAMIC) select TREE_RCU help This option selects the RCU implementation that is @@ -31,7 +31,7 @@ config PREEMPT_RCU config TINY_RCU bool - default y if !PREEMPTION && !SMP + default y if !PREEMPT_RCU && !SMP help This option selects the RCU implementation that is designed for UP systems from which real-time response @@ -65,6 +65,19 @@ config TREE_SRCU help This option selects the full-fledged version of SRCU. +config FORCE_NEED_SRCU_NMI_SAFE + bool "Force selection of NEED_SRCU_NMI_SAFE" + depends on !TINY_SRCU + depends on RCU_EXPERT + depends on ARCH_HAS_NMI_SAFE_THIS_CPU_OPS + select NEED_SRCU_NMI_SAFE + default n + help + This option forces selection of the NEED_SRCU_NMI_SAFE + Kconfig option, allowing testing of srcu_read_lock_nmisafe() + and srcu_read_unlock_nmisafe() on architectures (like x86) + that select the ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option. + config NEED_SRCU_NMI_SAFE def_bool HAVE_NMI && !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS && !TINY_SRCU @@ -85,9 +98,13 @@ config FORCE_TASKS_RCU idle, and user-mode execution as quiescent states. Not for manual selection in most cases. -config TASKS_RCU +config NEED_TASKS_RCU bool default n + +config TASKS_RCU + bool + default NEED_TASKS_RCU && PREEMPTION select IRQ_WORK config FORCE_TASKS_RUDE_RCU @@ -245,16 +262,24 @@ config RCU_NOCB_CPU workloads will incur significant increases in context-switch rates. - This option offloads callback invocation from the set of CPUs - specified at boot time by the rcu_nocbs parameter. For each - such CPU, a kthread ("rcuox/N") will be created to invoke - callbacks, where the "N" is the CPU being offloaded, and where - the "x" is "p" for RCU-preempt (PREEMPTION kernels) and "s" for - RCU-sched (!PREEMPTION kernels). Nothing prevents this kthread - from running on the specified CPUs, but (1) the kthreads may be - preempted between each callback, and (2) affinity or cgroups can - be used to force the kthreads to run on whatever set of CPUs is - desired. + This option offloads callback invocation from the set of + CPUs specified at boot time by the rcu_nocbs parameter. + For each such CPU, a kthread ("rcuox/N") will be created to + invoke callbacks, where the "N" is the CPU being offloaded, + and where the "x" is "p" for RCU-preempt (PREEMPTION kernels) + and "s" for RCU-sched (!PREEMPTION kernels). This option + also creates another kthread for each sqrt(nr_cpu_ids) CPUs + ("rcuog/N", where N is the first CPU in that group to come + online), which handles grace periods for its group. Nothing + prevents these kthreads from running on the specified CPUs, + but (1) the kthreads may be preempted between each callback, + and (2) affinity or cgroups can be used to force the kthreads + to run on whatever set of CPUs is desired. + + The sqrt(nr_cpu_ids) grouping may be overridden using the + rcutree.rcu_nocb_gp_stride kernel boot parameter. This can + be especially helpful for smaller numbers of CPUs, where + sqrt(nr_cpu_ids) can be a bit of a blunt instrument. Say Y here if you need reduced OS jitter, despite added overhead. Say N here if you are unsure. @@ -311,21 +336,27 @@ config RCU_LAZY depends on RCU_NOCB_CPU default n help - To save power, batch RCU callbacks and flush after delay, memory - pressure, or callback list growing too big. + To save power, batch RCU callbacks and delay starting the + corresponding grace period for multiple seconds. The grace + period will be started after this delay, in case of memory + pressure, or if the corresponding CPU's callback list grows + too large. - Requires rcu_nocbs=all to be set. + These delays happen only on rcu_nocbs CPUs, that is, CPUs + whose callbacks have been offloaded. - Use rcutree.enable_rcu_lazy=0 to turn it off at boot time. + Use the rcutree.enable_rcu_lazy=0 kernel-boot parameter to + globally disable these delays. config RCU_LAZY_DEFAULT_OFF bool "Turn RCU lazy invocation off by default" depends on RCU_LAZY default n help - Allows building the kernel with CONFIG_RCU_LAZY=y yet keep it default - off. Boot time param rcutree.enable_rcu_lazy=1 can be used to switch - it back on. + Build the kernel with CONFIG_RCU_LAZY=y, but cause the kernel + to boot with these energy-efficiency delays disabled. Use the + rcutree.enable_rcu_lazy=0 kernel-boot parameter to override + the this option at boot time, thus re-enabling these delays. config RCU_DOUBLE_CHECK_CB_TIME bool "RCU callback-batch backup time check" |