Loading...
/* SPDX-License-Identifier: GPL-2.0+ */ /* * RCU node combining tree definitions. These are used to compute * global attributes while avoiding common-case global contention. A key * property that these computations rely on is a tournament-style approach * where only one of the tasks contending a lower level in the tree need * advance to the next higher level. If properly configured, this allows * unlimited scalability while maintaining a constant level of contention * on the root node. * * This seemingly RCU-private file must be available to SRCU users * because the size of the TREE SRCU srcu_struct structure depends * on these definitions. * * Copyright IBM Corporation, 2017 * * Author: Paul E. McKenney <paulmck@linux.ibm.com> */ #ifndef __LINUX_RCU_NODE_TREE_H #define __LINUX_RCU_NODE_TREE_H #include <linux/math.h> /* * Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and * CONFIG_RCU_FANOUT_LEAF. * In theory, it should be possible to add more levels straightforwardly. * In practice, this did work well going from three levels to four. * Of course, your mileage may vary. */ #ifdef CONFIG_RCU_FANOUT #define RCU_FANOUT CONFIG_RCU_FANOUT #else /* #ifdef CONFIG_RCU_FANOUT */ # ifdef CONFIG_64BIT # define RCU_FANOUT 64 # else # define RCU_FANOUT 32 # endif #endif /* #else #ifdef CONFIG_RCU_FANOUT */ #ifdef CONFIG_RCU_FANOUT_LEAF #define RCU_FANOUT_LEAF CONFIG_RCU_FANOUT_LEAF #else /* #ifdef CONFIG_RCU_FANOUT_LEAF */ #define RCU_FANOUT_LEAF 16 #endif /* #else #ifdef CONFIG_RCU_FANOUT_LEAF */ #define RCU_FANOUT_1 (RCU_FANOUT_LEAF) #define RCU_FANOUT_2 (RCU_FANOUT_1 * RCU_FANOUT) #define RCU_FANOUT_3 (RCU_FANOUT_2 * RCU_FANOUT) #define RCU_FANOUT_4 (RCU_FANOUT_3 * RCU_FANOUT) #if NR_CPUS <= RCU_FANOUT_1 # define RCU_NUM_LVLS 1 # define NUM_RCU_LVL_0 1 # define NUM_RCU_NODES NUM_RCU_LVL_0 # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0 } # define RCU_NODE_NAME_INIT { "rcu_node_0" } # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" } #elif NR_CPUS <= RCU_FANOUT_2 # define RCU_NUM_LVLS 2 # define NUM_RCU_LVL_0 1 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1) # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1 } # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" } # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" } #elif NR_CPUS <= RCU_FANOUT_3 # define RCU_NUM_LVLS 3 # define NUM_RCU_LVL_0 1 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2) # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2 } # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" } # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" } #elif NR_CPUS <= RCU_FANOUT_4 # define RCU_NUM_LVLS 4 # define NUM_RCU_LVL_0 1 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3) # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) # define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3) # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2, NUM_RCU_LVL_3 } # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" } # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" } #else # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" #endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */ #endif /* __LINUX_RCU_NODE_TREE_H */ |