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From: "chengjian (D)" <cj.chengjian@huawei.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: <mingo@kernel.org>, <linux-kernel@vger.kernel.org>,
	<chenwandun@huawei.com>, <xiexiuqi@huawei.com>,
	<liwei391@huawei.com>, <huawei.libin@huawei.com>,
	<bobo.shaobowang@huawei.com>, <juri.lelli@redhat.com>,
	<vincent.guittot@linaro.org>
Subject: Re: [PATCH] sched/fair: Optimize select_idle_cpu
Date: Fri, 13 Dec 2019 09:51:30 +0800	[thread overview]
Message-ID: <52112146-a4ee-d09f-b61e-9aa35e2e5298@huawei.com> (raw)
In-Reply-To: <20191212150429.GZ2827@hirez.programming.kicks-ass.net>


On 2019/12/12 23:04, Peter Zijlstra wrote:
> On Thu, Dec 12, 2019 at 10:41:02PM +0800, Cheng Jian wrote:
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 08a233e97a01..16a29b570803 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -5834,6 +5834,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
>>   	s64 delta;
>>   	int this = smp_processor_id();
>>   	int cpu, nr = INT_MAX, si_cpu = -1;
>> +	struct cpumask cpus;
> NAK, you must not put a cpumask on stack.
>
> .

Hi, Peter

     I saw the same work in select_idle_core, and I was wondering why 
the per_cpu variable was

needed for this yesterday. Now I think I probably understand : cpumask 
may be too large,

putting it on the stack may cause overflow. Is this correct ?

     I'm sorry I made a mistake like this. I will fix it in v2

     Thank you very much.


         -- Cheng Jian




  reply	other threads:[~2019-12-13  1:51 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-12 14:41 [PATCH] sched/fair: Optimize select_idle_cpu Cheng Jian
2019-12-12 14:56 ` chengjian (D)
2019-12-12 15:04 ` Peter Zijlstra
2019-12-13  1:51   ` chengjian (D) [this message]
2019-12-13  8:10     ` Peter Zijlstra
2019-12-12 15:24 ` Peter Zijlstra
2019-12-12 15:44   ` Valentin Schneider
2019-12-13  9:47     ` chengjian (D)
2019-12-13  9:57   ` chengjian (D)
2019-12-13 11:28     ` Valentin Schneider
2019-12-13 12:09       ` Peter Zijlstra
2019-12-13 12:20         ` Valentin Schneider

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