linux-kernel - Re: [PATCH part2 v2 0/8] Arrange hotpluggable memory as ZONE

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Message-ID: <525C5727.7000603@zytor.com>
Date:	Mon, 14 Oct 2013 13:42:15 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>, Tejun Heo <tj@...nel.org>
CC:	Zhang Yanfei <zhangyanfei.yes@...il.com>,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>,
	Toshi Kani <toshi.kani@...com>, Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH part2 v2 0/8] Arrange hotpluggable memory as ZONE_MOVABLE

On 10/14/2013 01:37 PM, Yinghai Lu wrote:
>>
>> Optimizing NUMA boot just requires moving the heavy lifting to
>> appropriate NUMA nodes.  It doesn't require that early boot phase
>> should strictly follow NUMA node boundaries.
> 
> At end of day, I like to see all numa system (ram/cpu/pci) could have
> non boot nodes to be hot-removed logically. with any boot command
> line.
> 

I don't think that is realistic without hardware support, simply because
all it takes is a single page of kernel locked memory to prevent a page
from being removed.  The only realistic way around that, I believe, is
to remove the identity-mapping in the kernel, but it still has all kinds
of funnies involving devices and DMA.

	-hpa

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