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rcu: Limit rcu_capacity[] size to RCU_NUM_LVLS items

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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>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Alexander Gordeev 2015-06-03 08:18:28 +02:00 committed by Paul E. McKenney
parent a6d77081e2
commit 05b84aec46
2 changed files with 6 additions and 8 deletions
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12
kernel/rcu/tree.c
View file

@ -3998,19 +3998,19 @@ static void __init rcu_init_one(struct rcu_state *rsp,
"rcu_node_0", "rcu_node_0",
"rcu_node_1", "rcu_node_1",
"rcu_node_2", "rcu_node_2",
"rcu_node_3" }; /* Match MAX_RCU_LVLS */ "rcu_node_3" };
static const char * const fqs[] = { static const char * const fqs[] = {
"rcu_node_fqs_0", "rcu_node_fqs_0",
"rcu_node_fqs_1", "rcu_node_fqs_1",
"rcu_node_fqs_2", "rcu_node_fqs_2",
"rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */ "rcu_node_fqs_3" };
static u8 fl_mask = 0x1; static u8 fl_mask = 0x1;
int cpustride = 1; int cpustride = 1;
int i; int i;
int j; int j;
struct rcu_node *rnp; 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. */ /* Silence gcc 4.8 false positive about array index out of range. */
if (rcu_num_lvls <= 0 || rcu_num_lvls > RCU_NUM_LVLS) if (rcu_num_lvls <= 0 || rcu_num_lvls > RCU_NUM_LVLS)
@ -4082,7 +4082,7 @@ static void __init rcu_init_geometry(void)
{ {
ulong d; ulong d;
int i; int i;
int rcu_capacity[MAX_RCU_LVLS]; int rcu_capacity[RCU_NUM_LVLS];
/* /*
* Initialize any unspecified boot parameters. * Initialize any unspecified boot parameters.
@ -4122,14 +4122,14 @@ static void __init rcu_init_geometry(void)
* with the given number of levels. * with the given number of levels.
*/ */
rcu_capacity[0] = rcu_fanout_leaf; 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; rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT;
/* /*
* The tree must be able to accommodate the configured number of CPUs. * 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 this limit is exceeded than we have a serious problem elsewhere.
*/ */
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"); panic("rcu_init_geometry: rcu_capacity[] is too small");
/* Calculate the number of levels in the tree. */ /* Calculate the number of levels in the tree. */

2
kernel/rcu/tree.h
View file

@ -36,8 +36,6 @@
* Of course, your mileage may vary. * Of course, your mileage may vary.
*/ */
#define MAX_RCU_LVLS 4
#ifdef CONFIG_RCU_FANOUT #ifdef CONFIG_RCU_FANOUT
#define RCU_FANOUT CONFIG_RCU_FANOUT #define RCU_FANOUT CONFIG_RCU_FANOUT
#else /* #ifdef CONFIG_RCU_FANOUT */ #else /* #ifdef CONFIG_RCU_FANOUT */