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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>
hifive-unleashed-5.1
Rik van Riel 2015-05-14 22:59:36 -04:00 committed by Ingo Molnar
parent 80ed87c8a9
commit c1ceac6276
1 changed files with 34 additions and 28 deletions
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62
kernel/sched/fair.c
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@ -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;
/* Task is moving out of the group's interleave set. */
if (node_isset(src_nid, numa_group->active_nodes))
return true;
return group_faults(p, dst_nid) < group_faults(p, src_nid);
}
/* Migrating away from the preferred node is always bad. */
/* Migrating away from the preferred node is bad. */
if (src_nid == p->numa_preferred_nid)
return true;
return task_faults(p, dst_nid) < task_faults(p, src_nid);
/* Encourage migration to the preferred node. */
if (dst_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;
}
#else