linux-kernel - Re: [PATCH] kthread: ensure locality of task

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Message-ID: <alpine.DEB.2.10.1401290957350.23856@nuc>
Date:	Wed, 29 Jan 2014 09:58:04 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	David Rientjes <rientjes@...gle.com>
cc:	Nishanth Aravamudan <nacc@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Anton Blanchard <anton@...ba.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	Jan Kara <jack@...e.cz>, Thomas Gleixner <tglx@...utronix.de>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	linux-mm@...ck.org, Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Ben Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH] kthread: ensure locality of task_struct allocations

On Wed, 29 Jan 2014, David Rientjes wrote:

> > diff --git a/kernel/kthread.c b/kernel/kthread.c
> > index b5ae3ee..8573e4e 100644
> > --- a/kernel/kthread.c
> > +++ b/kernel/kthread.c
> > @@ -217,7 +217,7 @@ int tsk_fork_get_node(struct task_struct *tsk)
> >  	if (tsk == kthreadd_task)
> >  		return tsk->pref_node_fork;
> >  #endif
> > -	return numa_node_id();
> > +	return numa_mem_id();
>
> I'm wondering why return NUMA_NO_NODE wouldn't have the same effect and
> prefer the local node?
>

The idea here seems to be that the allocation may occur from a cpu that is
different from where the process will run later on.

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