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Kernels built with CONFIG_RCU_STRICT_GRACE_PERIOD=y can experience significant lock contention due to RCU's resulting focus on ending grace periods as soon as possible. This is OK, but only if there are not very many CPUs. This commit therefore puts this Kconfig option off-limits to systems with more than four CPUs. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
133 lines
4.1 KiB
Plaintext
133 lines
4.1 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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#
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# RCU-related debugging configuration options
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#
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menu "RCU Debugging"
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config PROVE_RCU
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def_bool PROVE_LOCKING
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config PROVE_RCU_LIST
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bool "RCU list lockdep debugging"
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depends on PROVE_RCU && RCU_EXPERT
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default n
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help
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Enable RCU lockdep checking for list usages. By default it is
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turned off since there are several list RCU users that still
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need to be converted to pass a lockdep expression. To prevent
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false-positive splats, we keep it default disabled but once all
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users are converted, we can remove this config option.
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config TORTURE_TEST
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tristate
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default n
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config RCU_SCALE_TEST
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tristate "performance tests for RCU"
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depends on DEBUG_KERNEL
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select TORTURE_TEST
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select SRCU
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select TASKS_RCU
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select TASKS_RUDE_RCU
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select TASKS_TRACE_RCU
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default n
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help
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This option provides a kernel module that runs performance
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tests on the RCU infrastructure. The kernel module may be built
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after the fact on the running kernel to be tested, if desired.
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Say Y here if you want RCU performance tests to be built into
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the kernel.
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Say M if you want the RCU performance tests to build as a module.
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Say N if you are unsure.
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config RCU_TORTURE_TEST
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tristate "torture tests for RCU"
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depends on DEBUG_KERNEL
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select TORTURE_TEST
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select SRCU
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select TASKS_RCU
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select TASKS_RUDE_RCU
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select TASKS_TRACE_RCU
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default n
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help
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This option provides a kernel module that runs torture tests
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on the RCU infrastructure. The kernel module may be built
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after the fact on the running kernel to be tested, if desired.
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Say Y here if you want RCU torture tests to be built into
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the kernel.
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Say M if you want the RCU torture tests to build as a module.
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Say N if you are unsure.
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config RCU_REF_SCALE_TEST
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tristate "Scalability tests for read-side synchronization (RCU and others)"
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depends on DEBUG_KERNEL
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select TORTURE_TEST
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select SRCU
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select TASKS_RCU
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select TASKS_RUDE_RCU
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select TASKS_TRACE_RCU
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default n
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help
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This option provides a kernel module that runs performance tests
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useful comparing RCU with various read-side synchronization mechanisms.
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The kernel module may be built after the fact on the running kernel to be
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tested, if desired.
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Say Y here if you want these performance tests built into the kernel.
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Say M if you want to build it as a module instead.
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Say N if you are unsure.
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config RCU_CPU_STALL_TIMEOUT
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int "RCU CPU stall timeout in seconds"
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depends on RCU_STALL_COMMON
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range 3 300
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default 21
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help
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If a given RCU grace period extends more than the specified
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number of seconds, a CPU stall warning is printed. If the
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RCU grace period persists, additional CPU stall warnings are
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printed at more widely spaced intervals.
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config RCU_TRACE
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bool "Enable tracing for RCU"
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depends on DEBUG_KERNEL
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default y if TREE_RCU
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select TRACE_CLOCK
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help
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This option enables additional tracepoints for ftrace-style
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event tracing.
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Say Y here if you want to enable RCU tracing
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Say N if you are unsure.
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config RCU_EQS_DEBUG
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bool "Provide debugging asserts for adding NO_HZ support to an arch"
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depends on DEBUG_KERNEL
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help
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This option provides consistency checks in RCU's handling of
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NO_HZ. These checks have proven quite helpful in detecting
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bugs in arch-specific NO_HZ code.
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Say N here if you need ultimate kernel/user switch latencies
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Say Y if you are unsure
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config RCU_STRICT_GRACE_PERIOD
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bool "Provide debug RCU implementation with short grace periods"
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depends on DEBUG_KERNEL && RCU_EXPERT && NR_CPUS <= 4
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default n
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select PREEMPT_COUNT if PREEMPT=n
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help
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Select this option to build an RCU variant that is strict about
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grace periods, making them as short as it can. This limits
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scalability, destroys real-time response, degrades battery
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lifetime and kills performance. Don't try this on large
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machines, as in systems with more than about 10 or 20 CPUs.
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But in conjunction with tools like KASAN, it can be helpful
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when looking for certain types of RCU usage bugs, for example,
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too-short RCU read-side critical sections.
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endmenu # "RCU Debugging"
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