3 files changed, 29 insertions, 8 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index fbfc4843063f..9d255bc0e278 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1537,6 +1537,7 @@ static void __sched_fork(struct task_struct *p)
 #ifdef CONFIG_NUMA_BALANCING
         if (p->mm && atomic_read(&p->mm->mm_users) == 1) {
                 p->mm->numa_next_scan = jiffies;
+                p->mm->numa_next_reset = jiffies;
                 p->mm->numa_scan_seq = 0;
         }
 
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index dd18087fd369..4b577863933f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -784,7 +784,8 @@ update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
  * numa task sample period in ms
  */
 unsigned int sysctl_numa_balancing_scan_period_min = 100;
-unsigned int sysctl_numa_balancing_scan_period_max = 100*16;
+unsigned int sysctl_numa_balancing_scan_period_max = 100*50;
+unsigned int sysctl_numa_balancing_scan_period_reset = 100*600;
 
 /* Portion of address space to scan in MB */
 unsigned int sysctl_numa_balancing_scan_size = 256;
@@ -806,20 +807,19 @@ static void task_numa_placement(struct task_struct *p)
 /*
  * Got a PROT_NONE fault for a page on @node.
  */
-void task_numa_fault(int node, int pages)
+void task_numa_fault(int node, int pages, bool migrated)
 {
         struct task_struct *p = current;
 
         /* FIXME: Allocate task-specific structure for placement policy here */
 
         /*
-         * Assume that as faults occur that pages are getting properly placed
-         * and fewer NUMA hints are required. Note that this is a big
-         * assumption, it assumes processes reach a steady steady with no
-         * further phase changes.
+         * If pages are properly placed (did not migrate) then scan slower.
+         * This is reset periodically in case of phase changes
          */
-        p->numa_scan_period = min(sysctl_numa_balancing_scan_period_max,
-                                p->numa_scan_period + jiffies_to_msecs(2));
+        if (!migrated)
+                p->numa_scan_period = min(sysctl_numa_balancing_scan_period_max,
+                        p->numa_scan_period + jiffies_to_msecs(10));
 
         task_numa_placement(p);
 }
@@ -858,6 +858,19 @@ void task_numa_work(struct callback_head *work)
                 return;
 
         /*
+         * Reset the scan period if enough time has gone by. Objective is that
+         * scanning will be reduced if pages are properly placed. As tasks
+         * can enter different phases this needs to be re-examined. Lacking
+         * proper tracking of reference behaviour, this blunt hammer is used.
+         */
+        migrate = mm->numa_next_reset;
+        if (time_after(now, migrate)) {
+                p->numa_scan_period = sysctl_numa_balancing_scan_period_min;
+                next_scan = now + msecs_to_jiffies(sysctl_numa_balancing_scan_period_reset);
+                xchg(&mm->numa_next_reset, next_scan);
+        }
+
+        /*
          * Enforce maximal scan/migration frequency..
          */
         migrate = mm->numa_next_scan;
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 48a68cc258c1..8906f90d6fa2 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -367,6 +367,13 @@ static struct ctl_table kern_table[] = {
                 .proc_handler   = proc_dointvec,
         },
         {
+                .procname       = "numa_balancing_scan_period_reset",
+                .data           = &sysctl_numa_balancing_scan_period_reset,
+                .maxlen         = sizeof(unsigned int),
+                .mode           = 0644,
+                .proc_handler   = proc_dointvec,
+        },
+        {
                 .procname       = "numa_balancing_scan_period_max_ms",
                 .data           = &sysctl_numa_balancing_scan_period_max,
                 .maxlen         = sizeof(unsigned int),