linux-kernel - Re: [PATCH v2] sched/deadline: reduce rq lock contention by eliminating locking of non-feasible target

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Message-ID: <20150326230300.GA3658@kernel>
Date:	Fri, 27 Mar 2015 07:03:00 +0800
From:	Wanpeng Li <wanpeng.li@...ux.intel.com>
To:	Juri Lelli <juri.lelli@....com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
Subject: Re: [PATCH v2] sched/deadline: reduce rq lock contention by
 eliminating locking of non-feasible target

Ping Juri, ;)
On Mon, Mar 23, 2015 at 05:02:13PM +0800, Wanpeng Li wrote:
>This patch adds checks that prevents futile attempts to move dl tasks to
>a CPU with active tasks of equal or earlier deadline. The same behavior as
>commit 80e3d87b2c55 ("sched/rt: Reduce rq lock contention by eliminating
>locking of non-feasible target") for rt class.
>
>Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
>---
>v1 -> v2:
> * use dl_time_before macro
>
> kernel/sched/deadline.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
>diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
>index 19d716e..f48d319 100644
>--- a/kernel/sched/deadline.c
>+++ b/kernel/sched/deadline.c
>@@ -955,7 +955,9 @@ select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
> 	    (p->nr_cpus_allowed > 1)) {
> 		int target = find_later_rq(p);
> 
>-		if (target != -1)
>+		if (target != -1 &&
>+			dl_time_before(p->dl.deadline,
>+				cpu_rq(target)->dl.earliest_dl.curr))
> 			cpu = target;
> 	}
> 	rcu_read_unlock();
>-- 
>1.9.1
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