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From:   subhra mazumdar <subhra.mazumdar@oracle.com>
To:     linux-kernel@vger.kernel.org
Cc:     peterz@infradead.org, mingo@redhat.com, steven.sistare@oracle.com,
        dhaval.giani@oracle.com, rohit.k.jain@oracle.com,
        daniel.lezcano@linaro.org
Subject: [PATCH 5/5] sched: SIS_CORE to disable idle core search
Date:   Thu, 28 Jun 2018 15:44:56 -0700
Message-Id: <20180628224456.13548-6-subhra.mazumdar@oracle.com>
In-Reply-To: <20180628224456.13548-1-subhra.mazumdar@oracle.com>
References: <20180628224456.13548-1-subhra.mazumdar@oracle.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Use SIS_CORE to disable idle core search. For some workloads
select_idle_core becomes a scalability bottleneck, removing it improves
throughput. Also there are workloads where disabling it can hurt latency,
so need to have an option.

Signed-off-by: subhra mazumdar <subhra.mazumdar@oracle.com>
---
 kernel/sched/fair.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 574cb14..33fbc47 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6464,9 +6464,11 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 	if (!sd)
 		return target;
 
-	i = select_idle_core(p, sd, target);
-	if ((unsigned)i < nr_cpumask_bits)
-		return i;
+	if (sched_feat(SIS_CORE)) {
+		i = select_idle_core(p, sd, target);
+		if ((unsigned)i < nr_cpumask_bits)
+			return i;
+	}
 
 	i = select_idle_cpu(p, sd, target);
 	if ((unsigned)i < nr_cpumask_bits)
-- 
2.9.3