---

yaml
---
r: 205421
b: refs/heads/master
c: 9d5efe0
h: refs/heads/master
i:
  205419: 515e4fa
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 83cd4fe27ad8446619b2e030b171b858501de87d
+refs/heads/master: 9d5efe05eb0c904545a28b19c18b949f23334de0

trunk/include/linux/sched.h

@@ -857,7 +857,7 @@ struct sched_group {
 	 * CPU power of this group, SCHED_LOAD_SCALE being max power for a
 	 * single CPU.
 	 */
-	unsigned int cpu_power;
+	unsigned int cpu_power, cpu_power_orig;
 
 	/*
 	 * The CPUs this group covers.

trunk/kernel/sched_fair.c

@@ -2285,13 +2285,6 @@ static void update_cpu_power(struct sched_domain *sd, int cpu)
 	unsigned long power = SCHED_LOAD_SCALE;
 	struct sched_group *sdg = sd->groups;
 
-	if (sched_feat(ARCH_POWER))
-		power *= arch_scale_freq_power(sd, cpu);
-	else
-		power *= default_scale_freq_power(sd, cpu);
-
-	power >>= SCHED_LOAD_SHIFT;
-
 	if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
 		if (sched_feat(ARCH_POWER))
 			power *= arch_scale_smt_power(sd, cpu);
@@ -2301,6 +2294,15 @@ static void update_cpu_power(struct sched_domain *sd, int cpu)
 		power >>= SCHED_LOAD_SHIFT;
 	}
 
+	sdg->cpu_power_orig = power;
+
+	if (sched_feat(ARCH_POWER))
+		power *= arch_scale_freq_power(sd, cpu);
+	else
+		power *= default_scale_freq_power(sd, cpu);
+
+	power >>= SCHED_LOAD_SHIFT;
+
 	power *= scale_rt_power(cpu);
 	power >>= SCHED_LOAD_SHIFT;
 
@@ -2333,6 +2335,31 @@ static void update_group_power(struct sched_domain *sd, int cpu)
 	sdg->cpu_power = power;
 }
 
+/*
+ * Try and fix up capacity for tiny siblings, this is needed when
+ * things like SD_ASYM_PACKING need f_b_g to select another sibling
+ * which on its own isn't powerful enough.
+ *
+ * See update_sd_pick_busiest() and check_asym_packing().
+ */
+static inline int
+fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
+{
+	/*
+	 * Only siblings can have significantly less than SCHED_LOAD_SCALE
+	 */
+	if (sd->level != SD_LV_SIBLING)
+		return 0;
+
+	/*
+	 * If ~90% of the cpu_power is still there, we're good.
+	 */
+	if (group->cpu_power * 32 < group->cpu_power_orig * 29)
+		return 1;
+
+	return 0;
+}
+
 /**
  * update_sg_lb_stats - Update sched_group's statistics for load balancing.
  * @sd: The sched_domain whose statistics are to be updated.
@@ -2426,6 +2453,8 @@ static inline void update_sg_lb_stats(struct sched_domain *sd,
 
 	sgs->group_capacity =
 		DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);
+	if (!sgs->group_capacity)
+		sgs->group_capacity = fix_small_capacity(sd, group);
 }
 
 /**
@@ -2724,8 +2753,9 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
  * find_busiest_queue - find the busiest runqueue among the cpus in group.
  */
 static struct rq *
-find_busiest_queue(struct sched_group *group, enum cpu_idle_type idle,
-		   unsigned long imbalance, const struct cpumask *cpus)
+find_busiest_queue(struct sched_domain *sd, struct sched_group *group,
+		   enum cpu_idle_type idle, unsigned long imbalance,
+		   const struct cpumask *cpus)
 {
 	struct rq *busiest = NULL, *rq;
 	unsigned long max_load = 0;
@@ -2736,6 +2766,9 @@ find_busiest_queue(struct sched_group *group, enum cpu_idle_type idle,
 		unsigned long capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
 		unsigned long wl;
 
+		if (!capacity)
+			capacity = fix_small_capacity(sd, group);
+
 		if (!cpumask_test_cpu(i, cpus))
 			continue;
 
@@ -2852,7 +2885,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
 		goto out_balanced;
 	}
 
-	busiest = find_busiest_queue(group, idle, imbalance, cpus);
+	busiest = find_busiest_queue(sd, group, idle, imbalance, cpus);
 	if (!busiest) {
 		schedstat_inc(sd, lb_nobusyq[idle]);
 		goto out_balanced;