* [PATCH] numa,sched: reduce conflict between fbq_classify_rq and migration
@ 2015-05-15 2:59 Rik van Riel
2015-05-19 7:23 ` [tip:sched/core] sched/numa: Reduce conflict between fbq_classify_rq() " tip-bot for Rik van Riel
0 siblings, 1 reply; 2+ messages in thread
From: Rik van Riel @ 2015-05-15 2:59 UTC (permalink / raw)
To: peterz; +Cc: mgorman, mingo, linux-kernel
It is possible for fbq_classify_rq to indicate that a CPU has tasks that
should be moved to another NUMA node, but for migrate_improves_locality
and migrate_degrades_locality to not identify those tasks.
This patch always gives preference to preferred node evaluations, and
only checks the number of faults when evaluating moves between two
non-preferred nodes on a larger NUMA system.
On a two node system, the number of faults is never evaluated. Either
a task is about to be pulled off its preferred node, or migrated onto
it.
Signed-off-by: Rik van Riel <riel@redhat.com>
---
kernel/sched/fair.c | 60 +++++++++++++++++++++++++++++------------------------
1 file changed, 33 insertions(+), 27 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ffeaa4105e48..9c9f225b14fc 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5467,10 +5467,15 @@ static int task_hot(struct task_struct *p, struct lb_env *env)
}
#ifdef CONFIG_NUMA_BALANCING
-/* Returns true if the destination node has incurred more faults */
+/*
+ * Returns true if the destination node is the preferred node.
+ * Needs to match fbq_classify_rq: if there is a runnable task
+ * that is not on its preferred node, we should identify it.
+ */
static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
{
struct numa_group *numa_group = rcu_dereference(p->numa_group);
+ unsigned long src_faults, dst_faults;
int src_nid, dst_nid;
if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults ||
@@ -5484,29 +5489,30 @@ static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
if (src_nid == dst_nid)
return false;
- if (numa_group) {
- /* Task is already in the group's interleave set. */
- if (node_isset(src_nid, numa_group->active_nodes))
- return false;
-
- /* Task is moving into the group's interleave set. */
- if (node_isset(dst_nid, numa_group->active_nodes))
- return true;
-
- return group_faults(p, dst_nid) > group_faults(p, src_nid);
- }
-
/* Encourage migration to the preferred node. */
if (dst_nid == p->numa_preferred_nid)
return true;
- return task_faults(p, dst_nid) > task_faults(p, src_nid);
+ /* Migrating away from the preferred node is bad. */
+ if (src_nid == p->numa_preferred_nid)
+ return false;
+
+ if (numa_group) {
+ src_faults = group_faults(p, src_nid);
+ dst_faults = group_faults(p, dst_nid);
+ } else {
+ src_faults = task_faults(p, src_nid);
+ dst_faults = task_faults(p, dst_nid);
+ }
+
+ return dst_faults > src_faults;
}
static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
{
struct numa_group *numa_group = rcu_dereference(p->numa_group);
+ unsigned long src_faults, dst_faults;
int src_nid, dst_nid;
if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER))
@@ -5521,23 +5527,23 @@ static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
if (src_nid == dst_nid)
return false;
- if (numa_group) {
- /* Task is moving within/into the group's interleave set. */
- if (node_isset(dst_nid, numa_group->active_nodes))
- return false;
+ /* Migrating away from the preferred node is bad. */
+ if (src_nid == p->numa_preferred_nid)
+ return true;
- /* Task is moving out of the group's interleave set. */
- if (node_isset(src_nid, numa_group->active_nodes))
- return true;
+ /* Encourage migration to the preferred node. */
+ if (dst_nid == p->numa_preferred_nid)
+ return false;
- return group_faults(p, dst_nid) < group_faults(p, src_nid);
+ if (numa_group) {
+ src_faults = group_faults(p, src_nid);
+ dst_faults = group_faults(p, dst_nid);
+ } else {
+ src_faults = task_faults(p, src_nid);
+ dst_faults = task_faults(p, dst_nid);
}
- /* Migrating away from the preferred node is always bad. */
- if (src_nid == p->numa_preferred_nid)
- return true;
-
- return task_faults(p, dst_nid) < task_faults(p, src_nid);
+ return dst_faults < src_faults;
}
#else
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [tip:sched/core] sched/numa: Reduce conflict between fbq_classify_rq() and migration
2015-05-15 2:59 [PATCH] numa,sched: reduce conflict between fbq_classify_rq and migration Rik van Riel
@ 2015-05-19 7:23 ` tip-bot for Rik van Riel
0 siblings, 0 replies; 2+ messages in thread
From: tip-bot for Rik van Riel @ 2015-05-19 7:23 UTC (permalink / raw)
To: linux-tip-commits; +Cc: mingo, riel, torvalds, peterz, hpa, tglx, linux-kernel
Commit-ID: c1ceac6276e4ee12e4129afd380db10fae0db7df
Gitweb: http://git.kernel.org/tip/c1ceac6276e4ee12e4129afd380db10fae0db7df
Author: Rik van Riel <riel@redhat.com>
AuthorDate: Thu, 14 May 2015 22:59:36 -0400
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 19 May 2015 08:39:19 +0200
sched/numa: Reduce conflict between fbq_classify_rq() and migration
It is possible for fbq_classify_rq() to indicate that a CPU has tasks that
should be moved to another NUMA node, but for migrate_improves_locality
and migrate_degrades_locality to not identify those tasks.
This patch always gives preference to preferred node evaluations, and
only checks the number of faults when evaluating moves between two
non-preferred nodes on a larger NUMA system.
On a two node system, the number of faults is never evaluated. Either
a task is about to be pulled off its preferred node, or migrated onto
it.
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: mgorman@suse.de
Link: http://lkml.kernel.org/r/20150514225936.35b91717@annuminas.surriel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/fair.c | 60 +++++++++++++++++++++++++++++------------------------
1 file changed, 33 insertions(+), 27 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a27d988..0d4632f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5663,10 +5663,15 @@ static int task_hot(struct task_struct *p, struct lb_env *env)
}
#ifdef CONFIG_NUMA_BALANCING
-/* Returns true if the destination node has incurred more faults */
+/*
+ * Returns true if the destination node is the preferred node.
+ * Needs to match fbq_classify_rq(): if there is a runnable task
+ * that is not on its preferred node, we should identify it.
+ */
static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
{
struct numa_group *numa_group = rcu_dereference(p->numa_group);
+ unsigned long src_faults, dst_faults;
int src_nid, dst_nid;
if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults ||
@@ -5680,29 +5685,30 @@ static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
if (src_nid == dst_nid)
return false;
- if (numa_group) {
- /* Task is already in the group's interleave set. */
- if (node_isset(src_nid, numa_group->active_nodes))
- return false;
-
- /* Task is moving into the group's interleave set. */
- if (node_isset(dst_nid, numa_group->active_nodes))
- return true;
-
- return group_faults(p, dst_nid) > group_faults(p, src_nid);
- }
-
/* Encourage migration to the preferred node. */
if (dst_nid == p->numa_preferred_nid)
return true;
- return task_faults(p, dst_nid) > task_faults(p, src_nid);
+ /* Migrating away from the preferred node is bad. */
+ if (src_nid == p->numa_preferred_nid)
+ return false;
+
+ if (numa_group) {
+ src_faults = group_faults(p, src_nid);
+ dst_faults = group_faults(p, dst_nid);
+ } else {
+ src_faults = task_faults(p, src_nid);
+ dst_faults = task_faults(p, dst_nid);
+ }
+
+ return dst_faults > src_faults;
}
static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
{
struct numa_group *numa_group = rcu_dereference(p->numa_group);
+ unsigned long src_faults, dst_faults;
int src_nid, dst_nid;
if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER))
@@ -5717,23 +5723,23 @@ static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
if (src_nid == dst_nid)
return false;
- if (numa_group) {
- /* Task is moving within/into the group's interleave set. */
- if (node_isset(dst_nid, numa_group->active_nodes))
- return false;
+ /* Migrating away from the preferred node is bad. */
+ if (src_nid == p->numa_preferred_nid)
+ return true;
- /* Task is moving out of the group's interleave set. */
- if (node_isset(src_nid, numa_group->active_nodes))
- return true;
+ /* Encourage migration to the preferred node. */
+ if (dst_nid == p->numa_preferred_nid)
+ return false;
- return group_faults(p, dst_nid) < group_faults(p, src_nid);
+ if (numa_group) {
+ src_faults = group_faults(p, src_nid);
+ dst_faults = group_faults(p, dst_nid);
+ } else {
+ src_faults = task_faults(p, src_nid);
+ dst_faults = task_faults(p, dst_nid);
}
- /* Migrating away from the preferred node is always bad. */
- if (src_nid == p->numa_preferred_nid)
- return true;
-
- return task_faults(p, dst_nid) < task_faults(p, src_nid);
+ return dst_faults < src_faults;
}
#else
^ permalink raw reply related [flat|nested] 2+ messages in thread
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2015-05-15 2:59 [PATCH] numa,sched: reduce conflict between fbq_classify_rq and migration Rik van Riel
2015-05-19 7:23 ` [tip:sched/core] sched/numa: Reduce conflict between fbq_classify_rq() " tip-bot for Rik van Riel
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