[PATCH v3 3/7] sched: rotate the cpu search window for better spread

[subhra mazumdar]

Rotate the cpu search window for better spread of threads. This will ensure
an idle cpu will quickly be found if one exists.

Signed-off-by: subhra mazumdar <subhra.mazum...@oracle.com>
---
 kernel/sched/fair.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b58f08f..c1ca88e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6188,7 +6188,7 @@ static int select_idle_cpu(struct task_struct *p, struct 
sched_domain *sd, int t
        u64 avg_cost, avg_idle;
        u64 time, cost;
        s64 delta;
-       int cpu, limit, floor, nr = INT_MAX;
+       int cpu, limit, floor, target_tmp, nr = INT_MAX;
 
        this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
        if (!this_sd)
@@ -6219,9 +6219,15 @@ static int select_idle_cpu(struct task_struct *p, struct 
sched_domain *sd, int t
                }
        }
 
+       if (per_cpu(next_cpu, target) != -1)
+               target_tmp = per_cpu(next_cpu, target);
+       else
+               target_tmp = target;
+
        time = local_clock();
 
-       for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
+       for_each_cpu_wrap(cpu, sched_domain_span(sd), target_tmp) {
+               per_cpu(next_cpu, target) = cpu;
                if (!--nr)
                        return -1;
                if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
-- 
2.9.3