linux-kernel - Re: [patch v4 01/18] sched: set SD_PREFER_SIBLING on MC domain to reduce a domain level

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Date:	Fri, 15 Feb 2013 13:38:19 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alex Shi <alex.shi@...el.com>
Cc:	torvalds@...ux-foundation.org, mingo@...hat.com,
	tglx@...utronix.de, akpm@...ux-foundation.org,
	arjan@...ux.intel.com, bp@...en8.de, pjt@...gle.com,
	namhyung@...nel.org, efault@....de, vincent.guittot@...aro.org,
	gregkh@...uxfoundation.org, preeti@...ux.vnet.ibm.com,
	viresh.kumar@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [patch v4 01/18] sched: set SD_PREFER_SIBLING on MC domain to
 reduce a domain level

On Wed, 2013-02-13 at 21:22 +0800, Alex Shi wrote:
> No, the flags set on MC/CPU domain, but is checked in their parents
> balancing, like in NUMA domain.
> Without the flag, will cause NUMA domain imbalance. like on my 2
> sockets
> NHM EP: 3 of 4 tasks were assigned on socket 0(lcpu, 10, 12, 14)
> 
> In this case, update_sd_pick_busiest() need a reduced group_capacity
> to
> return true:
>         if (sgs->sum_nr_running > sgs->group_capacity)
>                 return true;
> then numa domain balancing get chance to start.

Ah, indeed. Its always better to include such 'obvious' problems in the
changelog :-)

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