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rcu: Cleanup rcu_init_geometry() code and arithmetics

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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: Alexander Gordeev <agordeev@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Alexander Gordeev 2015-06-03 08:18:25 +02:00 committed by Paul E. McKenney
parent 372b0ec24f
commit 679f9858b1
1 changed files with 10 additions and 14 deletions
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24
kernel/rcu/tree.c
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@ -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 levels in the tree. */
for (i = 1; nr_cpu_ids > rcu_capacity[i]; i++) {
}
rcu_num_lvls = i;
/* 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);
}
rcu_num_lvls = i;
for (j = i + 1; j <= MAX_RCU_LVLS; j++)
num_rcu_lvl[j] = 0;
break;
}
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;
}
/*