rcu: Expedite during suspend and resume only on smallish systems

Expedited grace periods are of dubious benefit on very large systems,
so this commit restricts their automated use during suspend and resume
to systems of 256 or fewer CPUs.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 45971118b4450e317e0e958a2be8772c4e7c7d9a..00d4de0102f724d6c1993c84ac301ff87e78d2cf 100644 (file)
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -3009,7 +3009,8 @@ static int rcu_pm_notify(struct notifier_block *self,
 {
        switch (action) {
        case PM_HIBERNATION_PREPARE:
-               rcu_expedited = 1;
+               if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */
+                       rcu_expedited = 1;
                break;
        case PM_POST_RESTORE:
                rcu_expedited = 0;