sched: convert idle_balance() to cpumask_var_t.

Impact: stack usage reduction

Dynamically allocating cpumasks (when CONFIG_CPUMASK_OFFSTACK) saves
space in the stack.  cpumask_var_t is just a struct cpumask for
!CONFIG_CPUMASK_OFFSTACK.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched.c b/kernel/sched.c
index 2f8ea99df16aba55baa19ab66fd19bcfeddac5e0..154a95fcea7e49afabaa0c41b8634a6a5abc9832 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3676,7 +3676,10 @@ static void idle_balance(int this_cpu, struct rq *this_rq)
        struct sched_domain *sd;
        int pulled_task = -1;
        unsigned long next_balance = jiffies + HZ;
-       cpumask_t tmpmask;
+       cpumask_var_t tmpmask;
+
+       if (!alloc_cpumask_var(&tmpmask, GFP_ATOMIC))
+               return;
 
        for_each_domain(this_cpu, sd) {
                unsigned long interval;
@@ -3687,7 +3690,7 @@ static void idle_balance(int this_cpu, struct rq *this_rq)
                if (sd->flags & SD_BALANCE_NEWIDLE)
                        /* If we've pulled tasks over stop searching: */
                        pulled_task = load_balance_newidle(this_cpu, this_rq,
-                                                          sd, &tmpmask);
+                                                          sd, tmpmask);
 
                interval = msecs_to_jiffies(sd->balance_interval);
                if (time_after(next_balance, sd->last_balance + interval))
@@ -3702,6 +3705,7 @@ static void idle_balance(int this_cpu, struct rq *this_rq)
                 */
                this_rq->next_balance = next_balance;
        }
+       free_cpumask_var(tmpmask);
 }
 
 /*