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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293/* 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 */