linux-kernel - Re: [PATCH V2] sched: Improve load balancing in the presence of idle CPUs

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Message-ID: <20150327042349.GA4950@kernel>
Date:	Fri, 27 Mar 2015 12:23:49 +0800
From:	Wanpeng Li <wanpeng.li@...ux.intel.com>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc:	peterz@...radead.org, mingo@...nel.org, riel@...hat.com,
	daniel.lezcano@...aro.org, vincent.guittot@...aro.org,
	srikar@...ux.vnet.ibm.com, pjt@...gle.com,
	benh@...nel.crashing.org, efault@....de,
	linux-kernel@...r.kernel.org, iamjoonsoo.kim@....com,
	svaidy@...ux.vnet.ibm.com, tim.c.chen@...ux.intel.com,
	morten.rasmussen@....com, jason.low2@...com,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
Subject: Re: [PATCH V2] sched: Improve load balancing in the presence of idle
 CPUs

Hi Preeti,
On Fri, Mar 27, 2015 at 10:03:21AM +0530, Preeti U Murthy wrote:
>is set to CPU_NOT_IDLE.
>
>""
>idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
>
>And,
>
>When nohz_idle_balance() is called, the state of idle of ILB CPU is
>checked before proceeding with load balancing on idle CPUs.
>
>""
>
>if (idle != CPU_IDLE ||
>             !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
>                 goto end;
>

This idle is the one caculated in run_rebalance_domains() before invoke 
rebalance_domains(), rebalance_domains() cannot modify this local
variable.

Regards,
Wanpeng Li 

>You see that nohz idle balancing gets aborted.
>
>Regards
>Preeti U Murthy
>
>
>
>> 
>> Regards,
>> Wanpeng Li 
>> 
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