linux-kernel - Re: [RFC PATCH] sched: Pass affine target cpu into wake

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Date:	Tue, 05 Jan 2010 10:48:06 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Mike Galbraith <efault@....de>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
Subject: Re: [RFC PATCH] sched: Pass affine target cpu into wake_affine

On Mon, 2010-01-04 at 17:03 +0800, Lin Ming wrote:
> commit a03ecf08d7bbdd979d81163ea13d194fe21ad339
> Author: Lin Ming <ming.m.lin@...el.com>
> Date:   Mon Jan 4 14:14:50 2010 +0800
> 
>     sched: Pass affine target cpu into wake_affine
>     
>     Since commit a1f84a3(sched: Check for an idle shared cache in select_task_rq_fair()),
>     the affine target maybe adjusted to any idle cpu in cache sharing domains
>     instead of current cpu.
>     But wake_affine still use current cpu to calculate load which is wrong.
>     
>     This patch passes affine cpu into wake_affine.
>     
>     Signed-off-by: Lin Ming <ming.m.lin@...el.com>

Mike,

Any comment of this patch?

Thanks,
Lin Ming

> ---
>  kernel/sched_fair.c |   29 ++++++++++++++---------------
>  1 files changed, 14 insertions(+), 15 deletions(-)
> 
> diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
> index 42ac3c9..0a6fa39 100644
> --- a/kernel/sched_fair.c
> +++ b/kernel/sched_fair.c
> @@ -1237,11 +1237,11 @@ static inline unsigned long effective_load(struct task_group *tg, int cpu,
>  
>  #endif
>  
> -static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
> +static int wake_affine(struct sched_domain *sd, struct task_struct *p, int affine_cpu, int sync)
>  {
>  	struct task_struct *curr = current;
> -	unsigned long this_load, load;
> -	int idx, this_cpu, prev_cpu;
> +	unsigned long affine_load, load;
> +	int idx, prev_cpu;
>  	unsigned long tl_per_task;
>  	unsigned int imbalance;
>  	struct task_group *tg;
> @@ -1249,10 +1249,9 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
>  	int balanced;
>  
>  	idx	  = sd->wake_idx;
> -	this_cpu  = smp_processor_id();
>  	prev_cpu  = task_cpu(p);
>  	load	  = source_load(prev_cpu, idx);
> -	this_load = target_load(this_cpu, idx);
> +	affine_load = target_load(affine_cpu, idx);
>  
>  	if (sync) {
>  	       if (sched_feat(SYNC_LESS) &&
> @@ -1275,7 +1274,7 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
>  		tg = task_group(current);
>  		weight = current->se.load.weight;
>  
> -		this_load += effective_load(tg, this_cpu, -weight, -weight);
> +		affine_load += effective_load(tg, affine_cpu, -weight, -weight);
>  		load += effective_load(tg, prev_cpu, 0, -weight);
>  	}
>  
> @@ -1285,16 +1284,16 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
>  	imbalance = 100 + (sd->imbalance_pct - 100) / 2;
>  
>  	/*
> -	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
> -	 * due to the sync cause above having dropped this_load to 0, we'll
> +	 * In low-load situations, where prev_cpu is idle and affine_cpu is idle
> +	 * due to the sync cause above having dropped affine_load to 0, we'll
>  	 * always have an imbalance, but there's really nothing you can do
>  	 * about that, so that's good too.
>  	 *
>  	 * Otherwise check if either cpus are near enough in load to allow this
> -	 * task to be woken on this_cpu.
> +	 * task to be woken on affine_cpu.
>  	 */
> -	balanced = !this_load ||
> -		100*(this_load + effective_load(tg, this_cpu, weight, weight)) <=
> +	balanced = !affine_load ||
> +		100*(affine_load + effective_load(tg, affine_cpu, weight, weight)) <=
>  		imbalance*(load + effective_load(tg, prev_cpu, 0, weight));
>  
>  	/*
> @@ -1306,11 +1305,11 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
>  		return 1;
>  
>  	schedstat_inc(p, se.nr_wakeups_affine_attempts);
> -	tl_per_task = cpu_avg_load_per_task(this_cpu);
> +	tl_per_task = cpu_avg_load_per_task(affine_cpu);
>  
>  	if (balanced ||
> -	    (this_load <= load &&
> -	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
> +	    (affine_load <= load &&
> +	     affine_load + target_load(prev_cpu, idx) <= tl_per_task)) {
>  		/*
>  		 * This domain has SD_WAKE_AFFINE and
>  		 * p is cache cold in this domain, and
> @@ -1544,7 +1543,7 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flag
>  			update_shares(tmp);
>  	}
>  
> -	if (affine_sd && wake_affine(affine_sd, p, sync))
> +	if (affine_sd && wake_affine(affine_sd, p, cpu, sync))
>  		return cpu;
>  
>  	while (sd) {
> 

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