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-rw-r--r--include/linux/sched.h7
-rw-r--r--kernel/sched/fair.c63
-rw-r--r--mm/mempolicy.c29
3 files changed, 71 insertions, 28 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5fb0cfb..5ab3b89 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1589,6 +1589,8 @@ extern void task_numa_fault(int last_node, int node, int pages, int flags);
extern pid_t task_numa_group_id(struct task_struct *p);
extern void set_numabalancing_state(bool enabled);
extern void task_numa_free(struct task_struct *p);
+extern bool should_numa_migrate_memory(struct task_struct *p, struct page *page,
+ int src_nid, int dst_cpu);
#else
static inline void task_numa_fault(int last_node, int node, int pages,
int flags)
@@ -1604,6 +1606,11 @@ static inline void set_numabalancing_state(bool enabled)
static inline void task_numa_free(struct task_struct *p)
{
}
+static inline bool should_numa_migrate_memory(struct task_struct *p,
+ struct page *page, int src_nid, int dst_cpu)
+{
+ return true;
+}
#endif
static inline struct pid *task_pid(struct task_struct *task)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1ee921f..eeabb33 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -954,6 +954,69 @@ static inline unsigned long group_weight(struct task_struct *p, int nid)
return 1000 * group_faults(p, nid) / p->numa_group->total_faults;
}
+bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
+ int src_nid, int dst_cpu)
+{
+ struct numa_group *ng = p->numa_group;
+ int dst_nid = cpu_to_node(dst_cpu);
+ int last_cpupid, this_cpupid;
+
+ this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
+
+ /*
+ * Multi-stage node selection is used in conjunction with a periodic
+ * migration fault to build a temporal task<->page relation. By using
+ * a two-stage filter we remove short/unlikely relations.
+ *
+ * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
+ * a task's usage of a particular page (n_p) per total usage of this
+ * page (n_t) (in a given time-span) to a probability.
+ *
+ * Our periodic faults will sample this probability and getting the
+ * same result twice in a row, given these samples are fully
+ * independent, is then given by P(n)^2, provided our sample period
+ * is sufficiently short compared to the usage pattern.
+ *
+ * This quadric squishes small probabilities, making it less likely we
+ * act on an unlikely task<->page relation.
+ */
+ last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
+ if (!cpupid_pid_unset(last_cpupid) &&
+ cpupid_to_nid(last_cpupid) != dst_nid)
+ return false;
+
+ /* Always allow migrate on private faults */
+ if (cpupid_match_pid(p, last_cpupid))
+ return true;
+
+ /* A shared fault, but p->numa_group has not been set up yet. */
+ if (!ng)
+ return true;
+
+ /*
+ * Do not migrate if the destination is not a node that
+ * is actively used by this numa group.
+ */
+ if (!node_isset(dst_nid, ng->active_nodes))
+ return false;
+
+ /*
+ * Source is a node that is not actively used by this
+ * numa group, while the destination is. Migrate.
+ */
+ if (!node_isset(src_nid, ng->active_nodes))
+ return true;
+
+ /*
+ * Both source and destination are nodes in active
+ * use by this numa group. Maximize memory bandwidth
+ * by migrating from more heavily used groups, to less
+ * heavily used ones, spreading the load around.
+ * Use a 1/4 hysteresis to avoid spurious page movement.
+ */
+ return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
+}
+
static unsigned long weighted_cpuload(const int cpu);
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 68d5c7f..784c11e 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2377,37 +2377,10 @@ int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long
/* Migrate the page towards the node whose CPU is referencing it */
if (pol->flags & MPOL_F_MORON) {
- int last_cpupid;
- int this_cpupid;
-
polnid = thisnid;
- this_cpupid = cpu_pid_to_cpupid(thiscpu, current->pid);
- /*
- * Multi-stage node selection is used in conjunction
- * with a periodic migration fault to build a temporal
- * task<->page relation. By using a two-stage filter we
- * remove short/unlikely relations.
- *
- * Using P(p) ~ n_p / n_t as per frequentist
- * probability, we can equate a task's usage of a
- * particular page (n_p) per total usage of this
- * page (n_t) (in a given time-span) to a probability.
- *
- * Our periodic faults will sample this probability and
- * getting the same result twice in a row, given these
- * samples are fully independent, is then given by
- * P(n)^2, provided our sample period is sufficiently
- * short compared to the usage pattern.
- *
- * This quadric squishes small probabilities, making
- * it less likely we act on an unlikely task<->page
- * relation.
- */
- last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
- if (!cpupid_pid_unset(last_cpupid) && cpupid_to_nid(last_cpupid) != thisnid) {
+ if (!should_numa_migrate_memory(current, page, curnid, thiscpu))
goto out;
- }
}
if (curnid != polnid)
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