linux-kernel - Re: [PATCH 1/3] sched, balancing: Update rq->max_idle_balance_cost whenever newidle balance is attempted

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Message-ID: <20140424120415.GS11096@twins.programming.kicks-ass.net>
Date:	Thu, 24 Apr 2014 14:04:15 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc:	Jason Low <jason.low2@...com>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, daniel.lezcano@...aro.org,
	alex.shi@...aro.org, efault@....de, vincent.guittot@...aro.org,
	morten.rasmussen@....com, aswin@...com, chegu_vinod@...com
Subject: Re: [PATCH 1/3] sched, balancing: Update rq->max_idle_balance_cost
 whenever newidle balance is attempted

On Thu, Apr 24, 2014 at 03:44:47PM +0530, Preeti U Murthy wrote:
> What about the update of next_balance field? See the code snippet below.
> This will also be skipped as a consequence of the commit e5fc6611 right?
> 
> 	   if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
>                  /*
>                   * We are going idle. next_balance may be set based on
>                   * a busy processor. So reset next_balance.
>                   */
>                  this_rq->next_balance = next_balance;
>          }
> 
> Also the comment in the above snippet does not look right to me.
> It says "we are going idle" but the condition checks for pulled_task.

Yeah, that's odd indeed. Ingo did that back in dd41f596cda0d, I suspect
its an error, but..

So I think that should become !pulled_task || time_after().
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