sched: convert nohz struct to cpumask_var_t.

Impact: (future) size reduction for large NR_CPUS.

Dynamically allocating cpumasks (when CONFIG_CPUMASK_OFFSTACK) saves
space for small nr_cpu_ids but big CONFIG_NR_CPUS.  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>

1 files changed, 16 insertions, 13 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 93309c3034de..2f8ea99df16a 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3758,10 +3758,9 @@ static void active_load_balance(struct rq *busiest_rq, int busiest_cpu)
 #ifdef CONFIG_NO_HZ
 static struct {
         atomic_t load_balancer;
-        cpumask_t cpu_mask;
+        cpumask_var_t cpu_mask;
 } nohz ____cacheline_aligned = {
         .load_balancer = ATOMIC_INIT(-1),
-        .cpu_mask = CPU_MASK_NONE,
 };
 
 /*
@@ -3789,7 +3788,7 @@ int select_nohz_load_balancer(int stop_tick)
         int cpu = smp_processor_id();
 
         if (stop_tick) {
-                cpu_set(cpu, nohz.cpu_mask);
+                cpumask_set_cpu(cpu, nohz.cpu_mask);
                 cpu_rq(cpu)->in_nohz_recently = 1;
 
                 /*
@@ -3803,7 +3802,7 @@ int select_nohz_load_balancer(int stop_tick)
                 }
 
                 /* time for ilb owner also to sleep */
-                if (cpus_weight(nohz.cpu_mask) == num_online_cpus()) {
+                if (cpumask_weight(nohz.cpu_mask) == num_online_cpus()) {
                         if (atomic_read(&nohz.load_balancer) == cpu)
                                 atomic_set(&nohz.load_balancer, -1);
                         return 0;
@@ -3816,10 +3815,10 @@ int select_nohz_load_balancer(int stop_tick)
                 } else if (atomic_read(&nohz.load_balancer) == cpu)
                         return 1;
         } else {
-                if (!cpu_isset(cpu, nohz.cpu_mask))
+                if (!cpumask_test_cpu(cpu, nohz.cpu_mask))
                         return 0;
 
-                cpu_clear(cpu, nohz.cpu_mask);
+                cpumask_clear_cpu(cpu, nohz.cpu_mask);
 
                 if (atomic_read(&nohz.load_balancer) == cpu)
                         if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
@@ -3930,12 +3929,13 @@ static void run_rebalance_domains(struct softirq_action *h)
          */
         if (this_rq->idle_at_tick &&
             atomic_read(&nohz.load_balancer) == this_cpu) {
-                cpumask_t cpus = nohz.cpu_mask;
                 struct rq *rq;
                 int balance_cpu;
 
-                cpu_clear(this_cpu, cpus);
-                for_each_cpu(balance_cpu, &cpus) {
+                for_each_cpu(balance_cpu, nohz.cpu_mask) {
+                        if (balance_cpu == this_cpu)
+                                continue;
+
                         /*
                          * If this cpu gets work to do, stop the load balancing
                          * work being done for other cpus. Next load
@@ -3973,7 +3973,7 @@ static inline void trigger_load_balance(struct rq *rq, int cpu)
                 rq->in_nohz_recently = 0;
 
                 if (atomic_read(&nohz.load_balancer) == cpu) {
-                        cpu_clear(cpu, nohz.cpu_mask);
+                        cpumask_clear_cpu(cpu, nohz.cpu_mask);
                         atomic_set(&nohz.load_balancer, -1);
                 }
 
@@ -3986,7 +3986,7 @@ static inline void trigger_load_balance(struct rq *rq, int cpu)
                          * TBD: Traverse the sched domains and nominate
                          * the nearest cpu in the nohz.cpu_mask.
                          */
-                        int ilb = first_cpu(nohz.cpu_mask);
+                        int ilb = cpumask_first(nohz.cpu_mask);
 
                         if (ilb < nr_cpu_ids)
                                 resched_cpu(ilb);
@@ -3998,7 +3998,7 @@ static inline void trigger_load_balance(struct rq *rq, int cpu)
          * cpus with ticks stopped, is it time for that to stop?
          */
         if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) == cpu &&
-            cpus_weight(nohz.cpu_mask) == num_online_cpus()) {
+            cpumask_weight(nohz.cpu_mask) == num_online_cpus()) {
                 resched_cpu(cpu);
                 return;
         }
@@ -4008,7 +4008,7 @@ static inline void trigger_load_balance(struct rq *rq, int cpu)
          * someone else, then no need raise the SCHED_SOFTIRQ
          */
         if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) != cpu &&
-            cpu_isset(cpu, nohz.cpu_mask))
+            cpumask_test_cpu(cpu, nohz.cpu_mask))
                 return;
 #endif
         if (time_after_eq(jiffies, rq->next_balance))
@@ -8309,6 +8309,9 @@ void __init sched_init(void)
 
         /* Allocate the nohz_cpu_mask if CONFIG_CPUMASK_OFFSTACK */
         alloc_bootmem_cpumask_var(&nohz_cpu_mask);
+#ifdef CONFIG_NO_HZ
+        alloc_bootmem_cpumask_var(&nohz.cpu_mask);
+#endif
 
         scheduler_running = 1;
 }