sched/core: Give DCE a fighting chance

All that fancy new Energy-Aware scheduling foo is hidden behind a
static_key, which is awesome if you have the stuff enabled in your
config.

However, when you lack all the prerequisites it doesn't make any sense
to pretend we'll ever actually run this, so provide a little more clue
to the compiler so it can more agressively delete the code.

   text    data     bss     dec     hex filename
  50297     976      96   51369    c8a9 defconfig-build/kernel/sched/fair.o
  49227     944      96   50267    c45b defconfig-build/kernel/sched/fair.o

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 50aa2aba69bd4daba02dd6e697a011f364b3f2da..b1374fbddd0d30ca687c7950d2d87b740ffbca51 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6607,7 +6607,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
        if (sd_flag & SD_BALANCE_WAKE) {
                record_wakee(p);
 
-               if (static_branch_unlikely(&sched_energy_present)) {
+               if (sched_energy_enabled()) {
                        new_cpu = find_energy_efficient_cpu(p, prev_cpu);
                        if (new_cpu >= 0)
                                return new_cpu;
@@ -8635,7 +8635,7 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
         */
        update_sd_lb_stats(env, &sds);
 
-       if (static_branch_unlikely(&sched_energy_present)) {
+       if (sched_energy_enabled()) {
                struct root_domain *rd = env->dst_rq->rd;
 
                if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index d04530bf251fed21dfa0e4bcc0711dee85c7323e..d27c1a5d4e25720bc222a448217934f8f21a974d 100644 (file)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2299,11 +2299,19 @@ unsigned long scale_irq_capacity(unsigned long util, unsigned long irq, unsigned
 #endif
 
 #if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
+
 #define perf_domain_span(pd) (to_cpumask(((pd)->em_pd->cpus)))
-#else
+
+DECLARE_STATIC_KEY_FALSE(sched_energy_present);
+
+static inline bool sched_energy_enabled(void)
+{
+       return static_branch_unlikely(&sched_energy_present);
+}
+
+#else /* ! (CONFIG_ENERGY_MODEL && CONFIG_CPU_FREQ_GOV_SCHEDUTIL) */
+
 #define perf_domain_span(pd) NULL
-#endif
+static inline bool sched_energy_enabled(void) { return false; }
 
-#ifdef CONFIG_SMP
-extern struct static_key_false sched_energy_present;
-#endif
+#endif /* CONFIG_ENERGY_MODEL && CONFIG_CPU_FREQ_GOV_SCHEDUTIL */

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 50c3fc316c5459b381e3fa9ee370dd3e12e3c40d..4ae9403420edccb07ff90ddf9fa1681fecb2e458 100644 (file)
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -201,8 +201,8 @@ sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
        return 1;
 }
 
-DEFINE_STATIC_KEY_FALSE(sched_energy_present);
 #if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
+DEFINE_STATIC_KEY_FALSE(sched_energy_present);
 unsigned int sysctl_sched_energy_aware = 1;
 DEFINE_MUTEX(sched_energy_mutex);
 bool sched_energy_update;