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From:   Barry Song <song.bao.hua@hisilicon.com>
To:     <vincent.guittot@linaro.org>, <mingo@redhat.com>,
        <peterz@infradead.org>, <dietmar.eggemann@arm.com>,
        <rostedt@goodmis.org>, <bsegall@google.com>, <mgorman@suse.de>
CC:     <valentin.schneider@arm.com>, <juri.lelli@redhat.com>,
        <bristot@redhat.com>, <linux-kernel@vger.kernel.org>,
        <guodong.xu@linaro.org>, <yangyicong@huawei.com>,
        <tangchengchang@huawei.com>, <linuxarm@huawei.com>,
        Barry Song <song.bao.hua@hisilicon.com>
Subject: [PATCH] sched: fair: don't depend on wake_wide if waker and wakee are already in same LLC
Date:   Wed, 26 May 2021 21:10:57 +1200
Message-ID: <20210526091057.1800-1-song.bao.hua@hisilicon.com>
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when waker and wakee are already in the same LLC, it is pointless to worry
about the competition caused by pulling wakee to waker's LLC domain.

Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
---
 kernel/sched/fair.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3248e24a90b0..cfb1bd47acc3 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6795,7 +6795,15 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
 			new_cpu = prev_cpu;
 		}
 
-		want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, p->cpus_ptr);
+		/*
+		 * we use wake_wide to make smarter pull and avoid cruel
+		 * competition because of jam-packed tasks in waker's LLC
+		 * domain. But if waker and wakee have been already in
+		 * same LLC domain, it seems it is pointless to depend
+		 * on wake_wide
+		 */
+		want_affine = (cpus_share_cache(cpu, prev_cpu) || !wake_wide(p)) &&
+				cpumask_test_cpu(cpu, p->cpus_ptr);
 	}
 
 	rcu_read_lock();
-- 
2.25.1