| Paul E. McKenney | f2425b4 | 2017-03-14 12:42:30 -0700 | [diff] [blame] | 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 program is free software; you can redistribute it and/or modify |
| 11 | * it under the terms of the GNU General Public License as published by |
| 12 | * the Free Software Foundation; either version 2 of the License, or |
| 13 | * (at your option) any later version. |
| 14 | * |
| 15 | * This program is distributed in the hope that it will be useful, |
| 16 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 17 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 18 | * GNU General Public License for more details. |
| 19 | * |
| 20 | * You should have received a copy of the GNU General Public License |
| 21 | * along with this program; if not, you can access it online at |
| 22 | * http://www.gnu.org/licenses/gpl-2.0.html. |
| 23 | * |
| 24 | * Copyright IBM Corporation, 2017 |
| 25 | * |
| 26 | * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
| 27 | */ |
| 28 | |
| 29 | #ifndef __LINUX_RCU_NODE_TREE_H |
| 30 | #define __LINUX_RCU_NODE_TREE_H |
| 31 | |
| 32 | /* |
| 33 | * Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and |
| 34 | * CONFIG_RCU_FANOUT_LEAF. |
| 35 | * In theory, it should be possible to add more levels straightforwardly. |
| 36 | * In practice, this did work well going from three levels to four. |
| 37 | * Of course, your mileage may vary. |
| 38 | */ |
| 39 | |
| 40 | #ifdef CONFIG_RCU_FANOUT |
| 41 | #define RCU_FANOUT CONFIG_RCU_FANOUT |
| 42 | #else /* #ifdef CONFIG_RCU_FANOUT */ |
| 43 | # ifdef CONFIG_64BIT |
| 44 | # define RCU_FANOUT 64 |
| 45 | # else |
| 46 | # define RCU_FANOUT 32 |
| 47 | # endif |
| 48 | #endif /* #else #ifdef CONFIG_RCU_FANOUT */ |
| 49 | |
| 50 | #ifdef CONFIG_RCU_FANOUT_LEAF |
| 51 | #define RCU_FANOUT_LEAF CONFIG_RCU_FANOUT_LEAF |
| 52 | #else /* #ifdef CONFIG_RCU_FANOUT_LEAF */ |
| 53 | #define RCU_FANOUT_LEAF 16 |
| 54 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_LEAF */ |
| 55 | |
| 56 | #define RCU_FANOUT_1 (RCU_FANOUT_LEAF) |
| 57 | #define RCU_FANOUT_2 (RCU_FANOUT_1 * RCU_FANOUT) |
| 58 | #define RCU_FANOUT_3 (RCU_FANOUT_2 * RCU_FANOUT) |
| 59 | #define RCU_FANOUT_4 (RCU_FANOUT_3 * RCU_FANOUT) |
| 60 | |
| 61 | #if NR_CPUS <= RCU_FANOUT_1 |
| 62 | # define RCU_NUM_LVLS 1 |
| 63 | # define NUM_RCU_LVL_0 1 |
| 64 | # define NUM_RCU_NODES NUM_RCU_LVL_0 |
| 65 | # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0 } |
| 66 | # define RCU_NODE_NAME_INIT { "rcu_node_0" } |
| 67 | # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" } |
| 68 | #elif NR_CPUS <= RCU_FANOUT_2 |
| 69 | # define RCU_NUM_LVLS 2 |
| 70 | # define NUM_RCU_LVL_0 1 |
| 71 | # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) |
| 72 | # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1) |
| 73 | # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1 } |
| 74 | # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" } |
| 75 | # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" } |
| 76 | #elif NR_CPUS <= RCU_FANOUT_3 |
| 77 | # define RCU_NUM_LVLS 3 |
| 78 | # define NUM_RCU_LVL_0 1 |
| 79 | # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) |
| 80 | # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) |
| 81 | # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2) |
| 82 | # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2 } |
| 83 | # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" } |
| 84 | # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" } |
| 85 | #elif NR_CPUS <= RCU_FANOUT_4 |
| 86 | # define RCU_NUM_LVLS 4 |
| 87 | # define NUM_RCU_LVL_0 1 |
| 88 | # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3) |
| 89 | # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) |
| 90 | # define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) |
| 91 | # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3) |
| 92 | # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2, NUM_RCU_LVL_3 } |
| 93 | # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" } |
| 94 | # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" } |
| 95 | #else |
| 96 | # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" |
| 97 | #endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */ |
| 98 | |
| Paul E. McKenney | f2425b4 | 2017-03-14 12:42:30 -0700 | [diff] [blame] | 99 | #endif /* __LINUX_RCU_NODE_TREE_H */ |