sched: provide per cpu-cgroup option to notify on migrations
On systems where CPUs may run asynchronously, task migrations
between CPUs running at grossly different speeds can cause
problems.
This change provides a mechanism to notify a subsystem
in the kernel if a task in a particular cgroup migrates to a
different CPU. Other subsystems (such as cpufreq) may then
register for this notifier to take appropriate action when
such a task is migrated.
The cgroup attribute to set for this behavior is
"notify_on_migrate" .
Change-Id: Ie1868249e53ef901b89c837fdc33b0ad0c0a4590
Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 8f32475..f8317df 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1604,6 +1604,7 @@
struct task_struct *next_task;
struct rq *lowest_rq;
int ret = 0;
+ bool moved = false;
if (!rq->rt.overloaded)
return 0;
@@ -1673,6 +1674,7 @@
deactivate_task(rq, next_task, 0);
set_task_cpu(next_task, lowest_rq->cpu);
+ moved = true;
activate_task(lowest_rq, next_task, 0);
ret = 1;
@@ -1683,6 +1685,11 @@
out:
put_task_struct(next_task);
+ if (moved && task_notify_on_migrate(next_task))
+ atomic_notifier_call_chain(&migration_notifier_head,
+ cpu_of(lowest_rq),
+ (void *)cpu_of(rq));
+
return ret;
}
@@ -1696,8 +1703,10 @@
static int pull_rt_task(struct rq *this_rq)
{
int this_cpu = this_rq->cpu, ret = 0, cpu;
- struct task_struct *p;
+ struct task_struct *p = NULL;
struct rq *src_rq;
+ bool moved = false;
+ int src_cpu = 0;
if (likely(!rt_overloaded(this_rq)))
return 0;
@@ -1758,6 +1767,10 @@
deactivate_task(src_rq, p, 0);
set_task_cpu(p, this_cpu);
activate_task(this_rq, p, 0);
+
+ moved = true;
+ src_cpu = cpu_of(src_rq);
+
/*
* We continue with the search, just in
* case there's an even higher prio task
@@ -1769,6 +1782,11 @@
double_unlock_balance(this_rq, src_rq);
}
+ if (moved && task_notify_on_migrate(p))
+ atomic_notifier_call_chain(&migration_notifier_head,
+ this_cpu,
+ (void *)src_cpu);
+
return ret;
}