/* 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 <[email protected]> */ #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 … #else /* #ifdef CONFIG_RCU_FANOUT */ # ifdef CONFIG_64BIT #define RCU_FANOUT … # else #define RCU_FANOUT … # endif #endif /* #else #ifdef CONFIG_RCU_FANOUT */ #ifdef CONFIG_RCU_FANOUT_LEAF #define RCU_FANOUT_LEAF … #else /* #ifdef CONFIG_RCU_FANOUT_LEAF */ #define RCU_FANOUT_LEAF … #endif /* #else #ifdef CONFIG_RCU_FANOUT_LEAF */ #define RCU_FANOUT_1 … #define RCU_FANOUT_2 … #define RCU_FANOUT_3 … #define RCU_FANOUT_4 … #if NR_CPUS <= RCU_FANOUT_1 #define RCU_NUM_LVLS … #define NUM_RCU_LVL_0 … #define NUM_RCU_NODES … #define NUM_RCU_LVL_INIT … #define RCU_NODE_NAME_INIT … #define RCU_FQS_NAME_INIT … #elif NR_CPUS <= RCU_FANOUT_2 #define RCU_NUM_LVLS … #define NUM_RCU_LVL_0 … #define NUM_RCU_LVL_1 … #define NUM_RCU_NODES … #define NUM_RCU_LVL_INIT … #define RCU_NODE_NAME_INIT … #define RCU_FQS_NAME_INIT … #elif NR_CPUS <= RCU_FANOUT_3 #define RCU_NUM_LVLS … #define NUM_RCU_LVL_0 … #define NUM_RCU_LVL_1 … #define NUM_RCU_LVL_2 … #define NUM_RCU_NODES … #define NUM_RCU_LVL_INIT … #define RCU_NODE_NAME_INIT … #define RCU_FQS_NAME_INIT … #elif NR_CPUS <= RCU_FANOUT_4 #define RCU_NUM_LVLS … #define NUM_RCU_LVL_0 … #define NUM_RCU_LVL_1 … #define NUM_RCU_LVL_2 … #define NUM_RCU_LVL_3 … #define NUM_RCU_NODES … #define NUM_RCU_LVL_INIT … #define RCU_NODE_NAME_INIT … #define RCU_FQS_NAME_INIT … #else # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" #endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */ #endif /* __LINUX_RCU_NODE_TREE_H */
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