Commit 679f9858 authored by Alexander Gordeev's avatar Alexander Gordeev Committed by Paul E. McKenney
Browse files

rcu: Cleanup rcu_init_geometry() code and arithmetics 



This update simplifies rcu_init_geometry() code flow
and makes calculation of the total number of rcu_node
structures more easy to read.

The update relies on the fact num_rcu_lvl[] is never
accessed beyond rcu_num_lvls index by the rest of the
code. Therefore, there is no need initialize the whole
num_rcu_lvl[].

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 372b0ec2

kernel/rcu/tree.c

+10 −14
Original line number Diff line number Diff line
@@ -4082,7 +4082,6 @@ static void __init rcu_init_geometry(void) 
{

	ulong d;

	int i;

	int j;

	int rcu_capacity[MAX_RCU_LVLS + 1];



	/*
@@ -4135,24 +4134,21 @@ static void __init rcu_init_geometry(void) 
	if (nr_cpu_ids > rcu_capacity[MAX_RCU_LVLS])

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



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

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

		if (nr_cpu_ids <= rcu_capacity[i]) {

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

				int cap = rcu_capacity[i - j];

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

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

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

	}

	rcu_num_lvls = i;

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

				num_rcu_lvl[j] = 0;

			break;



	/* 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];

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

	}



	/* Calculate the total number of rcu_node structures. */

	rcu_num_nodes = 0;

	for (i = 0; i <= MAX_RCU_LVLS; i++)

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

		rcu_num_nodes += num_rcu_lvl[i];

	rcu_num_nodes -= nr_cpu_ids;

}



/*

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