linux-kernel - Re: [PATCH v2 1/4] sched/deadline: Modify cpudl.free

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Date:	Thu, 20 Nov 2014 17:00:20 +0800
From:	Wanpeng Li <kernellwp@...il.com>
To:	"pang.xunlei" <pang.xunlei@...aro.org>,
	linux-kernel@...r.kernel.org
CC:	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Juri Lelli <juri.lelli@...il.com>,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
Subject: Re: [PATCH v2 1/4] sched/deadline: Modify cpudl.free_cpus to reflect
 rd->span

Hi,
On 11/19/14, 11:46 PM, pang.xunlei wrote:
> Currently, cpudl.free_cpus contains all cpus during init(see cpudl_init()),
> so when calling cpudl_find() we have to add rd->span cpumask(cpus_allowed is
> undependable when performing clustered scheduling using the cpuset) to avoid
> selecting the cpu outside current root domain, see find_later_rq().
>
> This patch adds cpudl_set_freecpu() to initialize cpudl.free_cpus when doing
> rq_attach_root(), so we can avoid the extra rd->span operation when calling
> cpudl_find().
>
> Signed-off-by: pang.xunlei <pang.xunlei@...aro.org>

Reviewed-by: Wanpeng Li <wanpeng.li@...ux.intel.com>

I think this patch solve one problem I meet in my progress to handle dl 
task migration during cpu hotplug. 
https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg770579.html

Regards,
Wanpeng Li

> ---
>   kernel/sched/core.c        |    2 ++
>   kernel/sched/cpudeadline.c |   18 ++++++++++++++----
>   kernel/sched/cpudeadline.h |    1 +
>   kernel/sched/deadline.c    |    3 ---
>   4 files changed, 17 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 240157c..1b417de 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5584,6 +5584,8 @@ static void rq_attach_root(struct rq *rq, struct root_domain *rd)
>   	rq->rd = rd;
>   
>   	cpumask_set_cpu(rq->cpu, rd->span);
> +	cpudl_set_freecpu(&rd->cpudl, rq->cpu);
> +
>   	if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
>   		set_rq_online(rq);
>   
> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> index 539ca3c..c79f0d7 100644
> --- a/kernel/sched/cpudeadline.c
> +++ b/kernel/sched/cpudeadline.c
> @@ -107,7 +107,9 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
>   	int best_cpu = -1;
>   	const struct sched_dl_entity *dl_se = &p->dl;
>   
> -	if (later_mask && cpumask_and(later_mask, later_mask, cp->free_cpus)) {
> +	if (later_mask &&
> +	    cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed) &&
> +	    cpumask_and(later_mask, later_mask, cpu_active_mask)) {
>   		best_cpu = cpumask_any(later_mask);
>   		goto out;
>   	} else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
> @@ -186,6 +188,16 @@ out:
>   }
>   
>   /*
> + * cpudl_set_freecpu - Set the cpudl.free_cpus
> + * @cp: the cpudl max-heap context
> + * @cpu: rd attached cpu
> + */
> +void cpudl_set_freecpu(struct cpudl *cp, int cpu)
> +{
> +	cpumask_set_cpu(cpu, cp->free_cpus);
> +}
> +
> +/*
>    * cpudl_init - initialize the cpudl structure
>    * @cp: the cpudl max-heap context
>    */
> @@ -203,7 +215,7 @@ int cpudl_init(struct cpudl *cp)
>   	if (!cp->elements)
>   		return -ENOMEM;
>   
> -	if (!alloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {
> +	if (!zalloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {
>   		kfree(cp->elements);
>   		return -ENOMEM;
>   	}
> @@ -211,8 +223,6 @@ int cpudl_init(struct cpudl *cp)
>   	for_each_possible_cpu(i)
>   		cp->elements[i].idx = IDX_INVALID;
>   
> -	cpumask_setall(cp->free_cpus);
> -
>   	return 0;
>   }
>   
> diff --git a/kernel/sched/cpudeadline.h b/kernel/sched/cpudeadline.h
> index 020039b..4a10a65 100644
> --- a/kernel/sched/cpudeadline.h
> +++ b/kernel/sched/cpudeadline.h
> @@ -24,6 +24,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
>   	       struct cpumask *later_mask);
>   void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid);
>   int cpudl_init(struct cpudl *cp);
> +void cpudl_set_freecpu(struct cpudl *cp, int cpu);
>   void cpudl_cleanup(struct cpudl *cp);
>   #endif /* CONFIG_SMP */
>   
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 5285332..bd83272 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1187,9 +1187,6 @@ static int find_later_rq(struct task_struct *task)
>   	 * We have to consider system topology and task affinity
>   	 * first, then we can look for a suitable cpu.
>   	 */
> -	cpumask_copy(later_mask, task_rq(task)->rd->span);
> -	cpumask_and(later_mask, later_mask, cpu_active_mask);
> -	cpumask_and(later_mask, later_mask, &task->cpus_allowed);
>   	best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
>   			task, later_mask);
>   	if (best_cpu == -1)

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