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Subject[PATCH v3 07/10] sched/fair: Provide can_migrate_task_llc
Date
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
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