linux-kernel - Re: [PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent

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Date:	Mon, 25 Jul 2016 17:25:49 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Tejun Heo <tj@...nel.org>
Cc:	Dou Liyang <douly.fnst@...fujitsu.com>, cl@...ux.com,
	mika.j.penttila@...il.com, mingo@...hat.com, 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 v9 0/7] Make cpuid <-> nodeid mapping persistent

On Mon, 25 Jul 2016 20:11:51 -0400 Tejun Heo <tj@...nel.org> wrote:

> Hello, Andrew.
> 
> On Mon, Jul 25, 2016 at 04:20:22PM -0700, Andrew Morton wrote:
> > > When a pool workqueue is initialized, if its cpumask belongs to a node, its
> > > pool->node will be mapped to that node. And memory used by this workqueue will
> > > also be allocated on that node.
> > 
> > Plan B is to hunt down and fix up all the workqueue structures at
> > hotplug-time.  Has that option been evaluated?
> > 
> > Your fix is x86-only and this bug presumably affects other
> > architectures, yes?  I think a "Plan B" would fix all architectures?
> 
> Yeah, that was one of the early approaches.  The issue isn't limited
> to wq.  Any memory allocation can have similar issues of underlying
> node association changing and we don't have any synchronization
> mechanism around it.  It doesn't make any sense to make NUMA
> association dynamic when the consumer surface is vastly larger and
> there's nothing inherently dynamic about the association itself.

And other architectures?