diff options
| -rw-r--r-- | Documentation/kernel-parameters.txt | 6 | ||||
| -rw-r--r-- | init/Kconfig | 14 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 7 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 2 |
4 files changed, 12 insertions, 17 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 10a4fb80c033..f5582dcdf80d 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -3010,6 +3010,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted. the rcu_node combining tree. This only has effect when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set. + rcutree.rcu_fanout_exact= [KNL] + Disable autobalancing of the rcu_node combining + tree. This is used by rcutorture, and might + possibly be useful for architectures having high + cache-to-cache transfer latencies. + rcutree.rcu_fanout_leaf= [KNL] Increase the number of CPUs assigned to each leaf rcu_node structure. Useful for very large diff --git a/init/Kconfig b/init/Kconfig index 927210810189..0ec82362cfc0 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -611,20 +611,6 @@ config RCU_FANOUT_LEAF Take the default if unsure. -config RCU_FANOUT_EXACT - bool "Disable tree-based hierarchical RCU auto-balancing" - depends on TREE_RCU || PREEMPT_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. - config RCU_FAST_NO_HZ bool "Accelerate last non-dyntick-idle CPU's grace periods" depends on NO_HZ_COMMON && SMP diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 2f3cb5513ca3..b49c474e1fff 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -113,6 +113,9 @@ RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh); static struct rcu_state *rcu_state_p; LIST_HEAD(rcu_struct_flavors); +/* Control rcu_node-tree auto-balancing at boot time. */ +static bool rcu_fanout_exact; +module_param(rcu_fanout_exact, bool, 0444); /* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */ static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF; module_param(rcu_fanout_leaf, int, 0444); @@ -3956,13 +3959,13 @@ void rcu_scheduler_starting(void) /* * Compute the per-level fanout, either using the exact fanout specified - * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. + * or balancing the tree, depending on the rcu_fanout_exact boot parameter. */ static void __init rcu_init_levelspread(struct rcu_state *rsp) { int i; - if (IS_ENABLED(CONFIG_RCU_FANOUT_EXACT)) { + if (rcu_fanout_exact) { rsp->levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf; for (i = rcu_num_lvls - 2; i >= 0; i--) rsp->levelspread[i] = CONFIG_RCU_FANOUT; diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 58b1ebdc4387..eb460ec747ef 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -64,7 +64,7 @@ static void __init rcu_bootup_announce_oddness(void) (!IS_ENABLED(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 32)) pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n", CONFIG_RCU_FANOUT); - if (IS_ENABLED(CONFIG_RCU_FANOUT_EXACT)) + if (rcu_fanout_exact) pr_info("\tHierarchical RCU autobalancing is disabled.\n"); if (IS_ENABLED(CONFIG_RCU_FAST_NO_HZ)) pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n"); |