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

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Date:	Tue, 7 Apr 2015 17:38:57 +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] sched/deadline: reduce rq lock contention by
 eliminating locking of non-feasible target

Ping Peter, this patch is collected into this patchset https://lkml.org/lkml/2015/4/6/44
On Fri, Mar 27, 2015 at 07:03:00AM +0800, Wanpeng Li wrote:
>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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