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

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Message-ID: <20150519002314.GA2548@kernel>
Date:	Tue, 19 May 2015 08:23:15 +0800
From:	Wanpeng Li <wanpeng.li@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@....com>,
	linux-kernel@...r.kernel.org,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
Subject: Re: [PATCH v2 1/7] sched/deadline: fix try to pull pinned dl tasks
 in pull algorithm

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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