[tip:sched/numa] sched/numa: Fix NUMA_PULL_BIAS

From: tip-bot for Peter Zijlstra
Date: Fri Oct 12 2012 - 07:26:53 EST


Commit-ID: 5b1e7a5858fd9cbf5b2062d845db54b1750c6ca6
Gitweb: http://git.kernel.org/tip/5b1e7a5858fd9cbf5b2062d845db54b1750c6ca6
Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
AuthorDate: Fri, 5 Oct 2012 15:57:54 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 12 Oct 2012 12:07:17 +0200

sched/numa: Fix NUMA_PULL_BIAS

PULL_BIAS is broken, the intent was to only attempt a small bias when
the machine was otherwise balanced, hence the out_balanced label.

The problem is that a number of branches that decide we're completely
unbalanced also jump to the out_balanced label, causing undue numa
bias. The end result was that an unbalanced system of 8:1 would try
and move the 1 task towards the 8.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-3pzp0o6gemhb8t7fj8shscpo@xxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/fair.c | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 62d77ef..60be6bf 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4569,7 +4569,7 @@ find_busiest_group(struct lb_env *env, int *balance)

/* There is no busy sibling group to pull tasks from */
if (!sds.busiest || sds.busiest_nr_running == 0)
- goto out_balanced;
+ goto ret;

sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;

@@ -4591,14 +4591,14 @@ find_busiest_group(struct lb_env *env, int *balance)
* don't try and pull any tasks.
*/
if (sds.this_load >= sds.max_load)
- goto out_balanced;
+ goto ret;

/*
* Don't pull any tasks if this group is already above the domain
* average load.
*/
if (sds.this_load >= sds.avg_load)
- goto out_balanced;
+ goto ret;

if (env->idle == CPU_IDLE) {
/*
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/