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From:   Steve Sistare <steven.sistare@oracle.com>
To:     mingo@redhat.com, peterz@infradead.org
Cc:     subhra.mazumdar@oracle.com, dhaval.giani@oracle.com,
        daniel.m.jordan@oracle.com, pavel.tatashin@microsoft.com,
        matt@codeblueprint.co.uk, umgwanakikbuti@gmail.com,
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        valentin.schneider@arm.com, vincent.guittot@linaro.org,
        quentin.perret@arm.com, steven.sistare@oracle.com,
        linux-kernel@vger.kernel.org
Subject: [PATCH v3 07/10] sched/fair: Provide can_migrate_task_llc
Date:   Fri,  9 Nov 2018 04:50:37 -0800
Message-Id: <1541767840-93588-8-git-send-email-steven.sistare@oracle.com>
In-Reply-To: <1541767840-93588-1-git-send-email-steven.sistare@oracle.com>
References: <1541767840-93588-1-git-send-email-steven.sistare@oracle.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Define a simpler version of can_migrate_task called can_migrate_task_llc
which does not require a struct lb_env argument, and judges whether a
migration from one CPU to another within the same LLC should be allowed.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 kernel/sched/fair.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 453d280..dc6224d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7199,6 +7199,34 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env)
 }
 
 /*
+ * Return true if task @p can migrate from @rq to @dst_rq in the same LLC.
+ * No need to test for co-locality, and no need to test task_hot(), as sharing
+ * LLC provides cache warmth at that level.
+ */
+static bool
+can_migrate_task_llc(struct task_struct *p, struct rq *rq, struct rq *dst_rq)
+{
+	int dst_cpu = dst_rq->cpu;
+
+	lockdep_assert_held(&rq->lock);
+
+	if (throttled_lb_pair(task_group(p), cpu_of(rq), dst_cpu))
+		return false;
+
+	if (!cpumask_test_cpu(dst_cpu, &p->cpus_allowed)) {
+		schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
+		return false;
+	}
+
+	if (task_running(rq, p)) {
+		schedstat_inc(p->se.statistics.nr_failed_migrations_running);
+		return false;
+	}
+
+	return true;
+}
+
+/*
  * detach_task() -- detach the task for the migration from @src_rq to @dst_cpu.
  */
 static void detach_task(struct task_struct *p, struct rq *src_rq, int dst_cpu)
-- 
1.8.3.1