Commit f2425b4e authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

srcu: Move combining-tree definitions for SRCU's benefit 



This commit moves the C preprocessor code that defines the default shape
of the rcu_node combining tree to a new include/linux/rcu_node_tree.h
file as a first step towards enabling SRCU to create its own combining
tree, which in turn enables SRCU to implement per-CPU callback handling,
thus avoiding contention on the lock currently guarding the single list
of callbacks.  Note that users of SRCU still need to know the size of
the srcu_struct structure, hence include/linux rather than kernel/rcu.

This commit is code-movement only.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 8660b7d8

include/linux/rcu_node_tree.h

0 → 100644
+102 −0
Original line number Diff line number Diff line 
/*

 * 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.

 *

 * 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 */



extern int rcu_num_lvls;

extern int rcu_num_nodes;



#endif /* __LINUX_RCU_NODE_TREE_H */

kernel/rcu/tree.h

+1 −70
Original line number Diff line number Diff line
@@ -31,76 +31,7 @@ 
#include <linux/swait.h>

#include <linux/stop_machine.h>

#include <linux/rcu_segcblist.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 */



extern int rcu_num_lvls;

extern int rcu_num_nodes;

#include <linux/rcu_node_tree.h>



/*

 * Dynticks per-CPU state.

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