sched: convert falback_doms 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, 8 insertions, 6 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 526618fe4a78..42588ad93b25 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -7697,10 +7697,10 @@ static struct sched_domain_attr *dattr_cur;
 
 /*
  * Special case: If a kmalloc of a doms_cur partition (array of
- * cpumask_t) fails, then fallback to a single sched domain,
- * as determined by the single cpumask_t fallback_doms.
+ * cpumask) fails, then fallback to a single sched domain,
+ * as determined by the single cpumask fallback_doms.
  */
-static cpumask_t fallback_doms;
+static cpumask_var_t fallback_doms;
 
 void __attribute__((weak)) arch_update_cpu_topology(void)
 {
@@ -7719,7 +7719,7 @@ static int arch_init_sched_domains(const cpumask_t *cpu_map)
         ndoms_cur = 1;
         doms_cur = kmalloc(sizeof(cpumask_t), GFP_KERNEL);
         if (!doms_cur)
-                doms_cur = &fallback_doms;
+                doms_cur = fallback_doms;
         cpumask_andnot(doms_cur, cpu_map, cpu_isolated_map);
         dattr_cur = NULL;
         err = build_sched_domains(doms_cur);
@@ -7818,7 +7818,7 @@ match1:
 
         if (doms_new == NULL) {
                 ndoms_cur = 0;
-                doms_new = &fallback_doms;
+                doms_new = fallback_doms;
                 cpumask_andnot(&doms_new[0], cpu_online_mask, cpu_isolated_map);
                 WARN_ON_ONCE(dattr_new);
         }
@@ -7838,7 +7838,7 @@ match2:
         }
 
         /* Remember the new sched domains */
-        if (doms_cur != &fallback_doms)
+        if (doms_cur != fallback_doms)
                 kfree(doms_cur);
         kfree(dattr_cur);       /* kfree(NULL) is safe */
         doms_cur = doms_new;
@@ -8011,6 +8011,8 @@ void __init sched_init_smp(void)
                 BUG();
         sched_init_granularity();
         free_cpumask_var(non_isolated_cpus);
+
+        alloc_cpumask_var(&fallback_doms, GFP_KERNEL);
 }
 #else
 void __init sched_init_smp(void)