linux-kernel - Re: [PATCH v2 0/5] Add movablecore

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Date:	Fri, 30 Nov 2012 23:36:40 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
CC:	Jiang Liu <jiang.liu@...wei.com>, Mel Gorman <mgorman@...e.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Luck, Tony" <tony.luck@...el.com>,
	Tang Chen <tangchen@...fujitsu.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"rob@...dley.net" <rob@...dley.net>,
	"laijs@...fujitsu.com" <laijs@...fujitsu.com>,
	"wency@...fujitsu.com" <wency@...fujitsu.com>,
	"linfeng@...fujitsu.com" <linfeng@...fujitsu.com>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>,
	"minchan.kim@...il.com" <minchan.kim@...il.com>,
	"rientjes@...gle.com" <rientjes@...gle.com>,
	"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Len Brown <lenb@...nel.org>,
	"Wang, Frank" <frank.wang@...el.com>
Subject: Re: [PATCH v2 0/5] Add movablecore_map boot option

On 11/30/2012 11:15 AM, Yasuaki Ishimatsu wrote:
> Hi Jiang,
> 
>>
>> For the first issue, I think we could automatically convert pages
>> from movable zones into normal zones. Congyan from Fujitsu has provided
>> a patchset to manually convert pages from movable zones into normal zones,
>> I think we could extend that mechanism to automatically convert when
>> normal zones are under pressure by hooking into the slow page allocation
>> path.
>>
>> We rely on hardware features to solve the second and third issues.
>> Some new platforms provide a new RAS feature called "hardware memory
>> migration", which transparent migrate memory from one memory device
>> to another. With hardware memory migration, we could configure one
>> memory device on a NUMA node to host normal zone, and the other memory
>> devices to host movable zone. By this configuration, it won't cause
>> performance drop because each NUMA node still has local normal zone.
>> When trying to remove a memory device hosting normal zone, we just
>> need to find another spare memory device and use hardware memory migration
>> to transparently migrate memory content to the spare one. The drawback
>> is we have strong dependency on hardware features so it's not a common
>> solution for all architectures.
> 
> I agree with you. If BIOS and hardware support memory hotplug, OS should
> use them. But if OS cannot use them, we need to solve in OS. I think
> that our proposal which used ZONE_MOVABLE is first step for supporting
> memory hotplug.
Hi Yasuaki,
	It's true, we should start with first step then improve it.
Regards!
Gerry

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