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Subject[PATCH 60/63] mm: numa: revert temporarily disabling of NUMA migration
Date
From: Rik van Riel <riel@redhat.com>

With the scan rate code working (at least for multi-instance specjbb),
the large hammer that is "sched: Do not migrate memory immediately after
switching node" can be replaced with something smarter. Revert temporarily
migration disabling and all traces of numa_migrate_seq.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
include/linux/sched.h | 1 -
kernel/sched/core.c | 2 --
kernel/sched/fair.c | 25 +------------------------
mm/mempolicy.c | 12 ------------
4 files changed, 1 insertion(+), 39 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 918baf3..33c53d6 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1331,7 +1331,6 @@ struct task_struct {
#endif
#ifdef CONFIG_NUMA_BALANCING
int numa_scan_seq;
- int numa_migrate_seq;
unsigned int numa_scan_period;
unsigned int numa_scan_period_max;
unsigned long numa_migrate_retry;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3d60433..b7cf574 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1738,7 +1738,6 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)

p->node_stamp = 0ULL;
p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0;
- p->numa_migrate_seq = 1;
p->numa_scan_period = sysctl_numa_balancing_scan_delay;
p->numa_work.next = &p->numa_work;
p->numa_faults = NULL;
@@ -4505,7 +4504,6 @@ void sched_setnuma(struct task_struct *p, int nid)
p->sched_class->put_prev_task(rq, p);

p->numa_preferred_nid = nid;
- p->numa_migrate_seq = 1;

if (running)
p->sched_class->set_curr_task(rq);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 7c362f9..9bca073 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1261,16 +1261,8 @@ static void numa_migrate_preferred(struct task_struct *p)
{
/* Success if task is already running on preferred CPU */
p->numa_migrate_retry = 0;
- if (cpu_to_node(task_cpu(p)) == p->numa_preferred_nid) {
- /*
- * If migration is temporarily disabled due to a task migration
- * then re-enable it now as the task is running on its
- * preferred node and memory should migrate locally
- */
- if (!p->numa_migrate_seq)
- p->numa_migrate_seq++;
+ if (cpu_to_node(task_cpu(p)) == p->numa_preferred_nid)
return;
- }

/* This task has no NUMA fault statistics yet */
if (unlikely(p->numa_preferred_nid == -1))
@@ -1367,7 +1359,6 @@ static void task_numa_placement(struct task_struct *p)
if (p->numa_scan_seq == seq)
return;
p->numa_scan_seq = seq;
- p->numa_migrate_seq++;
p->numa_scan_period_max = task_scan_max(p);

/* If the task is part of a group prevent parallel updates to group stats */
@@ -4683,20 +4674,6 @@ static void move_task(struct task_struct *p, struct lb_env *env)
set_task_cpu(p, env->dst_cpu);
activate_task(env->dst_rq, p, 0);
check_preempt_curr(env->dst_rq, p, 0);
-#ifdef CONFIG_NUMA_BALANCING
- if (p->numa_preferred_nid != -1) {
- int src_nid = cpu_to_node(env->src_cpu);
- int dst_nid = cpu_to_node(env->dst_cpu);
-
- /*
- * If the load balancer has moved the task then limit
- * migrations from taking place in the short term in
- * case this is a short-lived migration.
- */
- if (src_nid != dst_nid && dst_nid != p->numa_preferred_nid)
- p->numa_migrate_seq = 0;
- }
-#endif
}

/*
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 07db309..e554587 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2348,18 +2348,6 @@ int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long
last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
if (!cpupid_pid_unset(last_cpupid) && cpupid_to_nid(last_cpupid) != thisnid)
goto out;
-
-#ifdef CONFIG_NUMA_BALANCING
- /*
- * If the scheduler has just moved us away from our
- * preferred node, do not bother migrating pages yet.
- * This way a short and temporary process migration will
- * not cause excessive memory migration.
- */
- if (thisnid != current->numa_preferred_nid &&
- !current->numa_migrate_seq)
- goto out;
-#endif
}

if (curnid != polnid)
--
1.8.1.4


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