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Subject[PATCH v2 6/9] rcu: Limit rcu_capacity[] size to RCU_NUM_LVLS items
Date
Number of items in rcu_capacity[] array is defined by macro
MAX_RCU_LVLS. However, that array is never accessed beyond
RCU_NUM_LVLS index. Therefore, we can limit the array to
RCU_NUM_LVLS items and eliminate MAX_RCU_LVLS. As result,
in most cases the memory is conserved.

Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
---
kernel/rcu/tree.c | 12 ++++++------
kernel/rcu/tree.h | 2 --
2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index b10e48e..f9be748 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3998,19 +3998,19 @@ static void __init rcu_init_one(struct rcu_state *rsp,
"rcu_node_0",
"rcu_node_1",
"rcu_node_2",
- "rcu_node_3" }; /* Match MAX_RCU_LVLS */
+ "rcu_node_3" };
static const char * const fqs[] = {
"rcu_node_fqs_0",
"rcu_node_fqs_1",
"rcu_node_fqs_2",
- "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */
+ "rcu_node_fqs_3" };
static u8 fl_mask = 0x1;
int cpustride = 1;
int i;
int j;
struct rcu_node *rnp;

- BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
+ BUILD_BUG_ON(RCU_NUM_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */

/* Silence gcc 4.8 false positive about array index out of range. */
if (rcu_num_lvls <= 0 || rcu_num_lvls > RCU_NUM_LVLS)
@@ -4082,7 +4082,7 @@ static void __init rcu_init_geometry(void)
{
ulong d;
int i;
- int rcu_capacity[MAX_RCU_LVLS];
+ int rcu_capacity[RCU_NUM_LVLS];

/*
* Initialize any unspecified boot parameters.
@@ -4109,7 +4109,7 @@ static void __init rcu_init_geometry(void)
* with the given number of levels.
*/
rcu_capacity[0] = rcu_fanout_leaf;
- for (i = 1; i < MAX_RCU_LVLS; i++)
+ for (i = 1; i < RCU_NUM_LVLS; i++)
rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT;

/*
@@ -4122,7 +4122,7 @@ static void __init rcu_init_geometry(void)
* the rcu_node masks. Complain and fall back to the compile-
* time values if these limits are exceeded.
*/
- if (nr_cpu_ids > rcu_capacity[MAX_RCU_LVLS - 1])
+ if (nr_cpu_ids > rcu_capacity[RCU_NUM_LVLS - 1])
panic("rcu_init_geometry: rcu_capacity[] is too small");
else if (rcu_fanout_leaf < RCU_FANOUT_LEAF ||
rcu_fanout_leaf > sizeof(unsigned long) * 8) {
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index a6faae5..d625e9f 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -36,8 +36,6 @@
* Of course, your mileage may vary.
*/

-#define MAX_RCU_LVLS 4
-
#ifdef CONFIG_RCU_FANOUT
#define RCU_FANOUT CONFIG_RCU_FANOUT
#else /* #ifdef CONFIG_RCU_FANOUT */
--
1.8.3.1


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