linux-kernel - Re: [PATCH v7 0/5] Make cpuid <-> nodeid mapping persistent

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Message-ID: <20160525203731.GJ3354@mtj.duckdns.org>
Date:	Wed, 25 May 2016 16:37:31 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Zhu Guihua <zhugh.fnst@...fujitsu.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, cl@...ux.com,
	mika.j.penttila@...il.com, mingo@...hat.com,
	akpm@...ux-foundation.org, rjw@...ysocki.net, hpa@...or.com,
	yasu.isimatu@...il.com, isimatu.yasuaki@...fujitsu.com,
	kamezawa.hiroyu@...fujitsu.com, izumi.taku@...fujitsu.com,
	gongzhaogang@...pur.com, len.brown@...el.com, lenb@...nel.org,
	tglx@...utronix.de, chen.tang@...ystack.cn, rafael@...nel.org,
	x86@...nel.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v7 0/5] Make cpuid <-> nodeid mapping persistent

On Mon, May 23, 2016 at 03:02:14PM +0800, Zhu Guihua wrote:
> We tried to do that. You can see our patch at
> http://www.gossamer-threads.com/lists/linux/kernel/2116748
> 
> But maintainer thought, we should establish persistent cpuid<->nodeid
> relationship,
> there is no need to change the map.
> 
> Cc TJ,
> Could we return to workqueue to fix this?

Workqueue is just one of symptoms.  We have the same problem for
memory allocation paths.  It's either keeping cpu <-> node mapping
persistent or hunting down every case which may be affected and build
likely costly synchronization construct around it.  It's not like we
have a lot of archs which support CPU hotplug and NUMA.

Thanks.

-- 
tejun