linux-kernel - Re: [PATCH v2 1/7] sched/deadline: fix try to pull pinned dl tasks in pull algorithm

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Date:	Tue, 26 May 2015 10:17:01 +0800
From:	Wanpeng Li <wanpeng.li@...mail.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>
Cc:	Juri Lelli <juri.lelli@....com>, linux-kernel@...r.kernel.org,
	Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH v2 1/7] sched/deadline: fix try to pull pinned dl tasks
 in pull algorithm

Ping,
On Tue, May 19, 2015 at 08:23:15AM +0800, Wanpeng Li wrote:
>Ping Peterz for this patchset, :)
>On Wed, May 13, 2015 at 02:01:01PM +0800, Wanpeng Li wrote:
>>Function pick_next_earliest_dl_task is used to pick earliest and pushable
>>dl task from overloaded cpus in pull algorithm, however, it traverses
>>runqueue rbtree instead of pushable task rbtree which is also ordered by
>>tasks' deadlines. This will result in getting no candidates from overloaded
>>cpus if all the dl tasks on the overloaded cpus are pinned. This patch fix
>>it by traversing pushable task rbtree which is also ordered by tasks'
>>deadlines.
>>
>>Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
>>---
>> kernel/sched/deadline.c | 29 ++++++++++++++++++++++++++++-
>> 1 file changed, 28 insertions(+), 1 deletion(-)
>>
>>diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
>>index 890ce95..f09f3ad 100644
>>--- a/kernel/sched/deadline.c
>>+++ b/kernel/sched/deadline.c
>>@@ -1230,6 +1230,33 @@ next_node:
>> 	return NULL;
>> }
>> 
>>+/*
>>+ * Return the earliest pushable rq's task, which is suitable to be executed
>>+ * on the cpu, NULL otherwse
>>+ */
>>+static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq,
>>+									int cpu)
>>+{
>>+	struct rb_node *next_node = rq->dl.pushable_dl_tasks_leftmost;
>>+	struct task_struct *p = NULL;
>>+
>>+	if (!has_pushable_dl_tasks(rq))
>>+		return NULL;
>>+
>>+next_node:
>>+	if (next_node) {
>>+		p = rb_entry(next_node, struct task_struct, pushable_dl_tasks);
>>+
>>+		if (pick_dl_task(rq, p, cpu))
>>+			return p;
>>+
>>+		next_node = rb_next(next_node);
>>+		goto next_node;
>>+	}
>>+
>>+	return NULL;
>>+}
>>+
>> static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
>> 
>> static int find_later_rq(struct task_struct *task)
>>@@ -1514,7 +1541,7 @@ static int pull_dl_task(struct rq *this_rq)
>> 		if (src_rq->dl.dl_nr_running <= 1)
>> 			goto skip;
>> 
>>-		p = pick_next_earliest_dl_task(src_rq, this_cpu);
>>+		p = pick_earliest_pushable_dl_task(src_rq, this_cpu);
>> 
>> 		/*
>> 		 * We found a task to be pulled if:
>>-- 
>>1.9.1


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