linux-kernel - Re: [PATCH] sched: update last_balance only when actually balanced

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Date:	Tue, 22 Jul 2014 11:46:39 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	linux-kernel@...r.kernel.org, Kirill Tkhai <ktkhai@...allels.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>, mingo@...nel.org,
	pjt@...gle.com
Subject: Re: [PATCH] sched: update last_balance only when actually balanced

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On 07/22/2014 08:04 AM, Peter Zijlstra wrote:

>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index
>> 45943b2..4f7fee2 100644 --- a/kernel/sched/fair.c +++
>> b/kernel/sched/fair.c @@ -7187,7 +7187,9 @@ static void
>> rebalance_domains(struct rq *rq, enum cpu_idle_type idle) */ idle
>> = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE; } -			sd->last_balance
>> = jiffies; +			/* Only update if we actually balanced. */ +			if
>> (continue_balancing) +				sd->last_balance = jiffies; interval =
>> get_sd_balance_interval(sd, idle != CPU_IDLE); } if
>> (need_serialize)
> 
> Did you actually see any difference with this patch?
> 
> The reason I'm asking is that the sched_domains are per cpu, so
> the above assignment is only visible to that particular cpu, not
> other cpus.

It was past 2AM, it may have been a placebo effect :)

Back to the drawing board, to figure out why the load balancing code
is not working quite as expected...

- -- 
All rights reversed
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