3 files changed, 29 insertions, 2 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 166144c04ef6..92744e3f1556 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -555,6 +555,14 @@ struct task_struct {
         unsigned long                   wakee_flip_decay_ts;
         struct task_struct              *last_wakee;
 
+        /*
+         * recent_used_cpu is initially set as the last CPU used by a task
+         * that wakes affine another task. Waker/wakee relationships can
+         * push tasks around a CPU where each wakeup moves to the next one.
+         * Tracking a recently used CPU allows a quick search for a recently
+         * used CPU that may be idle.
+         */
+        int                             recent_used_cpu;
         int                             wake_cpu;
 #endif
         int                             on_rq;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b40540e68104..36f113ac6353 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2461,6 +2461,7 @@ void wake_up_new_task(struct task_struct *p)
          * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
          * as we're not fully set-up yet.
          */
+        p->recent_used_cpu = task_cpu(p);
         __set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
 #endif
         rq = __task_rq_lock(p, &rf);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index db45b3554682..5eb3ffc9be84 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6197,7 +6197,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
 static int select_idle_sibling(struct task_struct *p, int prev, int target)
 {
         struct sched_domain *sd;
-        int i;
+        int i, recent_used_cpu;
 
         if (idle_cpu(target))
                 return target;
@@ -6208,6 +6208,21 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
         if (prev != target && cpus_share_cache(prev, target) && idle_cpu(prev))
                 return prev;
 
+        /* Check a recently used CPU as a potential idle candidate */
+        recent_used_cpu = p->recent_used_cpu;
+        if (recent_used_cpu != prev &&
+            recent_used_cpu != target &&
+            cpus_share_cache(recent_used_cpu, target) &&
+            idle_cpu(recent_used_cpu) &&
+            cpumask_test_cpu(p->recent_used_cpu, &p->cpus_allowed)) {
+                /*
+                 * Replace recent_used_cpu with prev as it is a potential
+                 * candidate for the next wake.
+                 */
+                p->recent_used_cpu = prev;
+                return recent_used_cpu;
+        }
+
         sd = rcu_dereference(per_cpu(sd_llc, target));
         if (!sd)
                 return target;
@@ -6375,9 +6390,12 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
 
         if (!sd) {
 pick_cpu:
-                if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
+                if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
                         new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
 
+                        if (want_affine)
+                                current->recent_used_cpu = cpu;
+                }
         } else {
                 new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
         }