1 /* 2 * RCU node combining tree definitions. These are used to compute 3 * global attributes while avoiding common-case global contention. A key 4 * property that these computations rely on is a tournament-style approach 5 * where only one of the tasks contending a lower level in the tree need 6 * advance to the next higher level. If properly configured, this allows 7 * unlimited scalability while maintaining a constant level of contention 8 * on the root node. 9 * 10 * This seemingly RCU-private file must be available to SRCU users 11 * because the size of the TREE SRCU srcu_struct structure depends 12 * on these definitions. 13 * 14 * This program is free software; you can redistribute it and/or modify 15 * it under the terms of the GNU General Public License as published by 16 * the Free Software Foundation; either version 2 of the License, or 17 * (at your option) any later version. 18 * 19 * This program is distributed in the hope that it will be useful, 20 * but WITHOUT ANY WARRANTY; without even the implied warranty of 21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 22 * GNU General Public License for more details. 23 * 24 * You should have received a copy of the GNU General Public License 25 * along with this program; if not, you can access it online at 26 * http://www.gnu.org/licenses/gpl-2.0.html. 27 * 28 * Copyright IBM Corporation, 2017 29 * 30 * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> 31 */ 32 33 #ifndef __LINUX_RCU_NODE_TREE_H 34 #define __LINUX_RCU_NODE_TREE_H 35 36 /* 37 * Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and 38 * CONFIG_RCU_FANOUT_LEAF. 39 * In theory, it should be possible to add more levels straightforwardly. 40 * In practice, this did work well going from three levels to four. 41 * Of course, your mileage may vary. 42 */ 43 44 #ifdef CONFIG_RCU_FANOUT 45 #define RCU_FANOUT CONFIG_RCU_FANOUT 46 #else /* #ifdef CONFIG_RCU_FANOUT */ 47 # ifdef CONFIG_64BIT 48 # define RCU_FANOUT 64 49 # else 50 # define RCU_FANOUT 32 51 # endif 52 #endif /* #else #ifdef CONFIG_RCU_FANOUT */ 53 54 #ifdef CONFIG_RCU_FANOUT_LEAF 55 #define RCU_FANOUT_LEAF CONFIG_RCU_FANOUT_LEAF 56 #else /* #ifdef CONFIG_RCU_FANOUT_LEAF */ 57 #define RCU_FANOUT_LEAF 16 58 #endif /* #else #ifdef CONFIG_RCU_FANOUT_LEAF */ 59 60 #define RCU_FANOUT_1 (RCU_FANOUT_LEAF) 61 #define RCU_FANOUT_2 (RCU_FANOUT_1 * RCU_FANOUT) 62 #define RCU_FANOUT_3 (RCU_FANOUT_2 * RCU_FANOUT) 63 #define RCU_FANOUT_4 (RCU_FANOUT_3 * RCU_FANOUT) 64 65 #if NR_CPUS <= RCU_FANOUT_1 66 # define RCU_NUM_LVLS 1 67 # define NUM_RCU_LVL_0 1 68 # define NUM_RCU_NODES NUM_RCU_LVL_0 69 # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0 } 70 # define RCU_NODE_NAME_INIT { "rcu_node_0" } 71 # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" } 72 #elif NR_CPUS <= RCU_FANOUT_2 73 # define RCU_NUM_LVLS 2 74 # define NUM_RCU_LVL_0 1 75 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) 76 # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1) 77 # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1 } 78 # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" } 79 # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" } 80 #elif NR_CPUS <= RCU_FANOUT_3 81 # define RCU_NUM_LVLS 3 82 # define NUM_RCU_LVL_0 1 83 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) 84 # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) 85 # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2) 86 # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2 } 87 # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" } 88 # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" } 89 #elif NR_CPUS <= RCU_FANOUT_4 90 # define RCU_NUM_LVLS 4 91 # define NUM_RCU_LVL_0 1 92 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3) 93 # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) 94 # define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) 95 # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3) 96 # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2, NUM_RCU_LVL_3 } 97 # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" } 98 # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" } 99 #else 100 # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" 101 #endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */ 102 103 #endif /* __LINUX_RCU_NODE_TREE_H */ 104
