linux-kernel - Re: [RFC][PATCH 1/5] sched, fair: Let minimally loaded cpu balance the group

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Message-ID: <20120502102541.GA22740@linux.vnet.ibm.com>
Date:	Wed, 2 May 2012 15:55:41 +0530
From:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	mingo@...nel.org, pjt@...gle.com, suresh.b.siddha@...el.com,
	efault@....de, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 1/5] sched, fair: Let minimally loaded cpu balance
 the group

* Peter Zijlstra <a.p.zijlstra@...llo.nl> [2012-05-01 20:14:31]:

> @@ -3795,12 +3796,11 @@ static inline void update_sg_lb_stats(st
> 
>  		/* Bias balancing toward cpus of our domain */
>  		if (local_group) {
> -			if (idle_cpu(i) && !first_idle_cpu) {
> -				first_idle_cpu = 1;
> +			load = target_load(i, load_idx);
> +			if (load < balance_load || idle_cpu(i)) {
> +				balance_load = load;

Let's say load_idx != 0 (ex: a busy cpu doing this load balance). In
that case, for a idle cpu, we could return non-zero load and hence this
would fail to select such a idle cpu? IOW :

		balance_load = 0 iff idle_cpu(i) ??

>  				balance_cpu = i;
>  			}
> -
> -			load = target_load(i, load_idx);
>  		} else {
>  			load = source_load(i, load_idx);
>  			if (load > max_cpu_load) {
> 
> 

- vatsa

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