rcu: Limit count of static data to the number of RCU levels

Although a number of RCU levels may be less than the current
maximum of four, some static data associated with each level
are allocated for all four levels. As result, the extra data
never get accessed and just wast memory. This update limits
count of allocated items to the number of used RCU levels.

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>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7226e25ba97fbbba62ebdb9bfd9ba46845b2ce40..e53bbc53bcd5fae9cad85728672078406694e018 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -124,13 +124,8 @@ module_param(rcu_fanout_exact, bool, 0444);
 static int rcu_fanout_leaf = RCU_FANOUT_LEAF;
 module_param(rcu_fanout_leaf, int, 0444);
 int rcu_num_lvls __read_mostly = RCU_NUM_LVLS;
-static int num_rcu_lvl[] = {  /* Number of rcu_nodes at specified level. */
-       NUM_RCU_LVL_0,
-       NUM_RCU_LVL_1,
-       NUM_RCU_LVL_2,
-       NUM_RCU_LVL_3,
-       NUM_RCU_LVL_4,
-};
+/* Number of rcu_nodes at specified level. */
+static int num_rcu_lvl[] = NUM_RCU_LVL_INIT;
 int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */
 
 /*
@@ -3994,16 +3989,8 @@ static void __init rcu_init_levelspread(int *levelspread, const int *levelcnt)
 static void __init rcu_init_one(struct rcu_state *rsp,
                struct rcu_data __percpu *rda)
 {
-       static const char * const buf[] = {
-               "rcu_node_0",
-               "rcu_node_1",
-               "rcu_node_2",
-               "rcu_node_3" };
-       static const char * const fqs[] = {
-               "rcu_node_fqs_0",
-               "rcu_node_fqs_1",
-               "rcu_node_fqs_2",
-               "rcu_node_fqs_3" };
+       static const char * const buf[] = RCU_NODE_NAME_INIT;
+       static const char * const fqs[] = RCU_FQS_NAME_INIT;
        static u8 fl_mask = 0x1;
 
        int levelcnt[RCU_NUM_LVLS];             /* # nodes in each level. */

diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 3413f3c5c8b253e12cf712b8777df173fdd7ccf3..d44856b6170afaf04cd82a0e1de712c4276102c9 100644 (file)
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -68,6 +68,9 @@
 #  define NUM_RCU_LVL_2              0
 #  define NUM_RCU_LVL_3              0
 #  define NUM_RCU_LVL_4              0
+#  define NUM_RCU_LVL_INIT    { NUM_RCU_LVL_0 }
+#  define RCU_NODE_NAME_INIT  { "rcu_node_0" }
+#  define RCU_FQS_NAME_INIT   { "rcu_node_fqs_0" }
 #elif NR_CPUS <= RCU_FANOUT_2
 #  define RCU_NUM_LVLS       2
 #  define NUM_RCU_LVL_0              1
@@ -75,6 +78,9 @@
 #  define NUM_RCU_LVL_2              (NR_CPUS)
 #  define NUM_RCU_LVL_3              0
 #  define NUM_RCU_LVL_4              0
+#  define NUM_RCU_LVL_INIT    { NUM_RCU_LVL_0, NUM_RCU_LVL_1 }
+#  define RCU_NODE_NAME_INIT  { "rcu_node_0", "rcu_node_1" }
+#  define RCU_FQS_NAME_INIT   { "rcu_node_fqs_0", "rcu_node_fqs_1" }
 #elif NR_CPUS <= RCU_FANOUT_3
 #  define RCU_NUM_LVLS       3
 #  define NUM_RCU_LVL_0              1
@@ -82,6 +88,9 @@
 #  define NUM_RCU_LVL_2              DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
 #  define NUM_RCU_LVL_3              (NR_CPUS)
 #  define NUM_RCU_LVL_4              0
+#  define NUM_RCU_LVL_INIT    { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2 }
+#  define RCU_NODE_NAME_INIT  { "rcu_node_0", "rcu_node_1", "rcu_node_2" }
+#  define RCU_FQS_NAME_INIT   { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" }
 #elif NR_CPUS <= RCU_FANOUT_4
 #  define RCU_NUM_LVLS       4
 #  define NUM_RCU_LVL_0              1
@@ -89,6 +98,9 @@
 #  define NUM_RCU_LVL_2              DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
 #  define NUM_RCU_LVL_3              DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
 #  define NUM_RCU_LVL_4              (NR_CPUS)
+#  define NUM_RCU_LVL_INIT    { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2, NUM_RCU_LVL_3 }
+#  define RCU_NODE_NAME_INIT  { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" }
+#  define RCU_FQS_NAME_INIT   { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" }
 #else
 # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
 #endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */