Eric Lee / smarc-fsl-linux-kernel

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include/linux/rcu_node_tree.h 4.34 KB
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f2425b4ef   Paul E. McKenney   srcu: Move combin... 
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  /*
   * 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.
   *
aaaad0bfa   Paul E. McKenney   rcu: Flag need fo... 
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   * 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.
   *
f2425b4ef   Paul E. McKenney   srcu: Move combin... 
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   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, you can access it online at
   * http://www.gnu.org/licenses/gpl-2.0.html.
   *
   * Copyright IBM Corporation, 2017
   *
   * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
   */
  
  #ifndef __LINUX_RCU_NODE_TREE_H
  #define __LINUX_RCU_NODE_TREE_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 */
f2425b4ef   Paul E. McKenney   srcu: Move combin... 
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  #endif /* __LINUX_RCU_NODE_TREE_H */