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

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Message-ID: <50B45318.3020605@cn.fujitsu.com>
Date:	Tue, 27 Nov 2012 13:43:52 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	wujianguo <wujianguo106@...il.com>
CC:	hpa@...or.com, akpm@...ux-foundation.org, rob@...dley.net,
	isimatu.yasuaki@...fujitsu.com, laijs@...fujitsu.com,
	wency@...fujitsu.com, linfeng@...fujitsu.com, jiang.liu@...wei.com,
	yinghai@...nel.org, kosaki.motohiro@...fujitsu.com,
	minchan.kim@...il.com, mgorman@...e.de, rientjes@...gle.com,
	rusty@...tcorp.com.au, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v2 0/5] Add movablecore_map boot option

On 11/27/2012 11:10 AM, wujianguo wrote:
> On 2012-11-23 18:44, Tang Chen wrote:
>> [What we are doing]
>> This patchset provide a boot option for user to specify ZONE_MOVABLE memory
>> map for each node in the system.
>>
>> movablecore_map=nn[KMG]@ss[KMG]
>>
>
> Hi Tang,
> 	DMA address can't be set as movable, if some one boot kernel with
> movablecore_map=4G@...00000 or other memory region that contains DMA address,
> system maybe boot failed. Should this case be handled or mentioned
> in the change log and kernel-parameters.txt?

Hi Wu,

Right, DMA address can't be set as movable. And I should have mentioned
it in the doc more clear. :)

Actually, the situation is not only for DMA address. Because we limited
the memblock allocation, even if users did not specified the DMA
address, but set too much memory as movable, which means there was too
little memory for kernel to use, kernel will also fail to boot.

I added the following info into doc, but obviously it was not clear
enough. :)
+		If kernelcore or movablecore is also specified,
+		movablecore_map will have higher priority to be
+		satisfied. So the administrator should be careful that
+		the amount of movablecore_map areas are not too large.
+		Otherwise kernel won't have enough memory to start.


And about how to fix it, as you said, we can handle the situation if
user specified DMA address as movable. But how to handle "too little
memory for kernel to start" case ?  Is there any info about how much
at least memory kernel needs ?


Thanks for the comments. :)

>
> Thanks,
> Jianguo Wu
>


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