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92 lines
3.7 KiB
92 lines
3.7 KiB
/* SPDX-License-Identifier: GPL-2.0+ */ |
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/* |
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* RCU node combining tree definitions. These are used to compute |
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* global attributes while avoiding common-case global contention. A key |
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* property that these computations rely on is a tournament-style approach |
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* where only one of the tasks contending a lower level in the tree need |
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* advance to the next higher level. If properly configured, this allows |
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* unlimited scalability while maintaining a constant level of contention |
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* on the root node. |
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* |
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* This seemingly RCU-private file must be available to SRCU users |
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* because the size of the TREE SRCU srcu_struct structure depends |
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* on these definitions. |
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* |
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* Copyright IBM Corporation, 2017 |
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* |
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* Author: Paul E. McKenney <[email protected]> |
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*/ |
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#ifndef __LINUX_RCU_NODE_TREE_H |
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#define __LINUX_RCU_NODE_TREE_H |
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#include <linux/math.h> |
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/* |
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* Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and |
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* CONFIG_RCU_FANOUT_LEAF. |
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* In theory, it should be possible to add more levels straightforwardly. |
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* In practice, this did work well going from three levels to four. |
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* Of course, your mileage may vary. |
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*/ |
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#ifdef CONFIG_RCU_FANOUT |
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#define RCU_FANOUT CONFIG_RCU_FANOUT |
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#else /* #ifdef CONFIG_RCU_FANOUT */ |
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# ifdef CONFIG_64BIT |
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# define RCU_FANOUT 64 |
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# else |
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# define RCU_FANOUT 32 |
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# endif |
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#endif /* #else #ifdef CONFIG_RCU_FANOUT */ |
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#ifdef CONFIG_RCU_FANOUT_LEAF |
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#define RCU_FANOUT_LEAF CONFIG_RCU_FANOUT_LEAF |
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#else /* #ifdef CONFIG_RCU_FANOUT_LEAF */ |
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#define RCU_FANOUT_LEAF 16 |
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#endif /* #else #ifdef CONFIG_RCU_FANOUT_LEAF */ |
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#define RCU_FANOUT_1 (RCU_FANOUT_LEAF) |
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#define RCU_FANOUT_2 (RCU_FANOUT_1 * RCU_FANOUT) |
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#define RCU_FANOUT_3 (RCU_FANOUT_2 * RCU_FANOUT) |
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#define RCU_FANOUT_4 (RCU_FANOUT_3 * RCU_FANOUT) |
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#if NR_CPUS <= RCU_FANOUT_1 |
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# define RCU_NUM_LVLS 1 |
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# define NUM_RCU_LVL_0 1 |
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# define NUM_RCU_NODES NUM_RCU_LVL_0 |
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# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0 } |
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# define RCU_NODE_NAME_INIT { "rcu_node_0" } |
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# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" } |
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#elif NR_CPUS <= RCU_FANOUT_2 |
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# define RCU_NUM_LVLS 2 |
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# define NUM_RCU_LVL_0 1 |
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# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) |
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# define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1) |
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# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1 } |
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# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" } |
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# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" } |
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#elif NR_CPUS <= RCU_FANOUT_3 |
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# define RCU_NUM_LVLS 3 |
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# define NUM_RCU_LVL_0 1 |
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# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) |
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# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) |
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# define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2) |
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# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2 } |
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# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" } |
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# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" } |
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#elif NR_CPUS <= RCU_FANOUT_4 |
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# define RCU_NUM_LVLS 4 |
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# define NUM_RCU_LVL_0 1 |
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# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3) |
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# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) |
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# define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) |
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# define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3) |
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# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2, NUM_RCU_LVL_3 } |
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# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" } |
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# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" } |
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#else |
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# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" |
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#endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */ |
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#endif /* __LINUX_RCU_NODE_TREE_H */
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