Commit 9618138b authored by Alexander Gordeev's avatar Alexander Gordeev Committed by Paul E. McKenney
Browse files

rcu: Simplify rcu_init_geometry() capacity arithmetics 



Current code suggests that introducing the extra level to
rcu_capacity[] array makes some of the arithmetic easier.
Well, in fact it appears rather confusing and unnecessary.

Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarAlexander Gordeev <agordeev@redhat.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 679f9858

kernel/rcu/tree.c

+8 −10
Original line number Diff line number Diff line
@@ -4082,7 +4082,7 @@ static void __init rcu_init_geometry(void) 
{

	ulong d;

	int i;

	int rcu_capacity[MAX_RCU_LVLS + 1];

	int rcu_capacity[MAX_RCU_LVLS];



	/*

	 * Initialize any unspecified boot parameters.
@@ -4119,29 +4119,27 @@ static void __init rcu_init_geometry(void) 


	/*

	 * Compute number of nodes that can be handled an rcu_node tree

	 * with the given number of levels.  Setting rcu_capacity[0] makes

	 * some of the arithmetic easier.

	 * with the given number of levels.

	 */

	rcu_capacity[0] = 1;

	rcu_capacity[1] = rcu_fanout_leaf;

	for (i = 2; i <= MAX_RCU_LVLS; i++)

	rcu_capacity[0] = rcu_fanout_leaf;

	for (i = 1; i < MAX_RCU_LVLS; i++)

		rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT;



	/*

	 * The tree must be able to accommodate the configured number of CPUs.

	 * If this limit is exceeded than we have a serious problem elsewhere.

	 */

	if (nr_cpu_ids > rcu_capacity[MAX_RCU_LVLS])

	if (nr_cpu_ids > rcu_capacity[MAX_RCU_LVLS - 1])

		panic("rcu_init_geometry: rcu_capacity[] is too small");



	/* Calculate the number of levels in the tree. */

	for (i = 1; nr_cpu_ids > rcu_capacity[i]; i++) {

	for (i = 0; nr_cpu_ids > rcu_capacity[i]; i++) {

	}

	rcu_num_lvls = i;

	rcu_num_lvls = i + 1;



	/* Calculate the number of rcu_nodes at each level of the tree. */

	for (i = 0; i < rcu_num_lvls; i++) {

		int cap = rcu_capacity[rcu_num_lvls - i];

		int cap = rcu_capacity[(rcu_num_lvls - 1) - i];

		num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap);

	}

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