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authorPeter Zijlstra <peterz@infradead.org>2011-11-10 13:01:10 +0100
committerIngo Molnar <mingo@elte.hu>2011-11-16 08:43:43 +0100
commit4dcfe1025b513c2c1da5bf5586adb0e80148f612 (patch)
tree1c0bf8ad4c09a3a618c471b6468873d8d8ed2117 /kernel/sched_fair.c
parentf1c6f1a7eed963ed233ba4c8b6fa8addb86c6ddc (diff)
downloadlinux-linaro-stable-4dcfe1025b513c2c1da5bf5586adb0e80148f612.tar.gz
sched: Avoid SMT siblings in select_idle_sibling() if possible
Avoid select_idle_sibling() from picking a sibling thread if there's an idle core that shares cache. This fixes SMT balancing in the increasingly common case where there's a shared cache core available to balance to. Tested-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Suresh Siddha <suresh.b.siddha@intel.com> Link: http://lkml.kernel.org/r/1321350377.1421.55.camel@twins Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_fair.c')
-rw-r--r--kernel/sched_fair.c42
1 files changed, 28 insertions, 14 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 7e51b5bb27cc..ba0e1f49a22f 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -2326,7 +2326,8 @@ static int select_idle_sibling(struct task_struct *p, int target)
int cpu = smp_processor_id();
int prev_cpu = task_cpu(p);
struct sched_domain *sd;
- int i;
+ struct sched_group *sg;
+ int i, smt = 0;
/*
* If the task is going to be woken-up on this cpu and if it is
@@ -2346,25 +2347,38 @@ static int select_idle_sibling(struct task_struct *p, int target)
* Otherwise, iterate the domains and find an elegible idle cpu.
*/
rcu_read_lock();
+again:
for_each_domain(target, sd) {
- if (!(sd->flags & SD_SHARE_PKG_RESOURCES))
- break;
+ if (!smt && (sd->flags & SD_SHARE_CPUPOWER))
+ continue;
- for_each_cpu_and(i, sched_domain_span(sd), tsk_cpus_allowed(p)) {
- if (idle_cpu(i)) {
- target = i;
- break;
+ if (!(sd->flags & SD_SHARE_PKG_RESOURCES)) {
+ if (!smt) {
+ smt = 1;
+ goto again;
}
+ break;
}
- /*
- * Lets stop looking for an idle sibling when we reached
- * the domain that spans the current cpu and prev_cpu.
- */
- if (cpumask_test_cpu(cpu, sched_domain_span(sd)) &&
- cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
- break;
+ sg = sd->groups;
+ do {
+ if (!cpumask_intersects(sched_group_cpus(sg),
+ tsk_cpus_allowed(p)))
+ goto next;
+
+ for_each_cpu(i, sched_group_cpus(sg)) {
+ if (!idle_cpu(i))
+ goto next;
+ }
+
+ target = cpumask_first_and(sched_group_cpus(sg),
+ tsk_cpus_allowed(p));
+ goto done;
+next:
+ sg = sg->next;
+ } while (sg != sd->groups);
}
+done:
rcu_read_unlock();
return target;