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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-05-08 21:00:28 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-07-02 12:33:21 -0700
commitcca6f3931920a7547d02e68adc2ca635bea5600c (patch)
tree31e2cd3d9e73f080ca78a89a6dba474c1987beee /kernel/rcutree.c
parentcc5df65b0370fc6aa2bfe3bb19e0451d5cafb99f (diff)
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rcu: Size rcu_node tree from nr_cpu_ids rather than NR_CPUS
The rcu_node tree array is sized based on compile-time constants, including NR_CPUS. Although this approach has worked well in the past, the recent trend by many distros to define NR_CPUS=4096 results in excessive grace-period-initialization latencies. This commit therefore substitutes the run-time computed nr_cpu_ids for the compile-time NR_CPUS when building the tree. This can result in much of the compile-time-allocated rcu_node array being unused. If this is a major problem, you are in a specialized situation anyway, so you can manually adjust the NR_CPUS, RCU_FANOUT, and RCU_FANOUT_LEAF kernel config parameters. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutree.c')
-rw-r--r--kernel/rcutree.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index a4c592b66e10..0fdbc5e07302 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -2675,7 +2675,7 @@ static void __init rcu_init_geometry(void)
{
int i;
int j;
- int n = NR_CPUS;
+ int n = nr_cpu_ids;
int rcu_capacity[MAX_RCU_LVLS + 1];
/* If the compile-time values are accurate, just leave. */