projects / linux-2.6-block.git / blame
| Commit | Line | Data |
|---|---|---|
| 5efd1d94 | 1 | /* SPDX-License-Identifier: GPL-2.0+ */ |
| f2425b4e PM |
2 | /* |
| 3 | * RCU node combining tree definitions. These are used to compute | |
| 4 | * global attributes while avoiding common-case global contention. A key | |
| 5 | * property that these computations rely on is a tournament-style approach | |
| 6 | * where only one of the tasks contending a lower level in the tree need | |
| 7 | * advance to the next higher level. If properly configured, this allows | |
| 8 | * unlimited scalability while maintaining a constant level of contention | |
| 9 | * on the root node. | |
| 10 | * | |
| aaaad0bf PM |
11 | * This seemingly RCU-private file must be available to SRCU users |
| 12 | * because the size of the TREE SRCU srcu_struct structure depends | |
| 13 | * on these definitions. | |
| 14 | * | |
| f2425b4e PM |
15 | * Copyright IBM Corporation, 2017 |
| 16 | * | |
| 5efd1d94 | 17 | * Author: Paul E. McKenney <paulmck@linux.ibm.com> |
| f2425b4e PM |
18 | */ |
| 19 | ||
| 20 | #ifndef __LINUX_RCU_NODE_TREE_H | |
| 21 | #define __LINUX_RCU_NODE_TREE_H | |
| 22 | ||
| 23 | /* | |
| 24 | * Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and | |
| 25 | * CONFIG_RCU_FANOUT_LEAF. | |
| 26 | * In theory, it should be possible to add more levels straightforwardly. | |
| 27 | * In practice, this did work well going from three levels to four. | |
| 28 | * Of course, your mileage may vary. | |
| 29 | */ | |
| 30 | ||
| 31 | #ifdef CONFIG_RCU_FANOUT | |
| 32 | #define RCU_FANOUT CONFIG_RCU_FANOUT | |
| 33 | #else /* #ifdef CONFIG_RCU_FANOUT */ | |
| 34 | # ifdef CONFIG_64BIT | |
| 35 | # define RCU_FANOUT 64 | |
| 36 | # else | |
| 37 | # define RCU_FANOUT 32 | |
| 38 | # endif | |
| 39 | #endif /* #else #ifdef CONFIG_RCU_FANOUT */ | |
| 40 | ||
| 41 | #ifdef CONFIG_RCU_FANOUT_LEAF | |
| 42 | #define RCU_FANOUT_LEAF CONFIG_RCU_FANOUT_LEAF | |
| 43 | #else /* #ifdef CONFIG_RCU_FANOUT_LEAF */ | |
| 44 | #define RCU_FANOUT_LEAF 16 | |
| 45 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_LEAF */ | |
| 46 | ||
| 47 | #define RCU_FANOUT_1 (RCU_FANOUT_LEAF) | |
| 48 | #define RCU_FANOUT_2 (RCU_FANOUT_1 * RCU_FANOUT) | |
| 49 | #define RCU_FANOUT_3 (RCU_FANOUT_2 * RCU_FANOUT) | |
| 50 | #define RCU_FANOUT_4 (RCU_FANOUT_3 * RCU_FANOUT) | |
| 51 | ||
| 52 | #if NR_CPUS <= RCU_FANOUT_1 | |
| 53 | # define RCU_NUM_LVLS 1 | |
| 54 | # define NUM_RCU_LVL_0 1 | |
| 55 | # define NUM_RCU_NODES NUM_RCU_LVL_0 | |
| 56 | # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0 } | |
| 57 | # define RCU_NODE_NAME_INIT { "rcu_node_0" } | |
| 58 | # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" } | |
| 59 | #elif NR_CPUS <= RCU_FANOUT_2 | |
| 60 | # define RCU_NUM_LVLS 2 | |
| 61 | # define NUM_RCU_LVL_0 1 | |
| 62 | # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) | |
| 63 | # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1) | |
| 64 | # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1 } | |
| 65 | # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" } | |
| 66 | # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" } | |
| 67 | #elif NR_CPUS <= RCU_FANOUT_3 | |
| 68 | # define RCU_NUM_LVLS 3 | |
| 69 | # define NUM_RCU_LVL_0 1 | |
| 70 | # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) | |
| 71 | # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) | |
| 72 | # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2) | |
| 73 | # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2 } | |
| 74 | # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" } | |
| 75 | # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" } | |
| 76 | #elif NR_CPUS <= RCU_FANOUT_4 | |
| 77 | # define RCU_NUM_LVLS 4 | |
| 78 | # define NUM_RCU_LVL_0 1 | |
| 79 | # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3) | |
| 80 | # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) | |
| 81 | # define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) | |
| 82 | # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3) | |
| 83 | # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2, NUM_RCU_LVL_3 } | |
| 84 | # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" } | |
| 85 | # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" } | |
| 86 | #else | |
| 87 | # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" | |
| 88 | #endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */ | |
| 89 | ||
| f2425b4e | 90 | #endif /* __LINUX_RCU_NODE_TREE_H */ |