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-rw-r--r--kernel/Kconfig.preempt62
1 files changed, 56 insertions, 6 deletions
diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index 9fdba03dc1fc..463f29743ea0 100644
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -52,10 +52,29 @@ config PREEMPT
endchoice
+choice
+ prompt "RCU Implementation"
+ default CLASSIC_RCU
+
+config CLASSIC_RCU
+ bool "Classic RCU"
+ help
+ This option selects the classic RCU implementation that is
+ designed for best read-side performance on non-realtime
+ systems.
+
+ Select this option if you are unsure.
+
+config TREE_RCU
+ bool "Tree-based hierarchical RCU"
+ help
+ This option selects the RCU implementation that is
+ designed for very large SMP system with hundreds or
+ thousands of CPUs.
+
config PREEMPT_RCU
bool "Preemptible RCU"
depends on PREEMPT
- default n
help
This option reduces the latency of the kernel by making certain
RCU sections preemptible. Normally RCU code is non-preemptible, if
@@ -64,16 +83,47 @@ config PREEMPT_RCU
now-naive assumptions about each RCU read-side critical section
remaining on a given CPU through its execution.
- Say N if you are unsure.
+endchoice
config RCU_TRACE
- bool "Enable tracing for RCU - currently stats in debugfs"
- depends on PREEMPT_RCU
- select DEBUG_FS
- default y
+ bool "Enable tracing for RCU"
+ depends on TREE_RCU || PREEMPT_RCU
help
This option provides tracing in RCU which presents stats
in debugfs for debugging RCU implementation.
Say Y here if you want to enable RCU tracing
Say N if you are unsure.
+
+config RCU_FANOUT
+ int "Tree-based hierarchical RCU fanout value"
+ range 2 64 if 64BIT
+ range 2 32 if !64BIT
+ depends on TREE_RCU
+ default 64 if 64BIT
+ default 32 if !64BIT
+ help
+ This option controls the fanout of hierarchical implementations
+ of RCU, allowing RCU to work efficiently on machines with
+ large numbers of CPUs. This value must be at least the cube
+ root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
+ systems and up to 262,144 for 64-bit systems.
+
+ Select a specific number if testing RCU itself.
+ Take the default if unsure.
+
+config RCU_FANOUT_EXACT
+ bool "Disable tree-based hierarchical RCU auto-balancing"
+ depends on TREE_RCU
+ default n
+ help
+ This option forces use of the exact RCU_FANOUT value specified,
+ regardless of imbalances in the hierarchy. This is useful for
+ testing RCU itself, and might one day be useful on systems with
+ strong NUMA behavior.
+
+ Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
+
+ Say n if unsure.
+
+