linux-kernel - Re: mmots: memory-hotplug: implement register_page_bootmem_info

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Message-ID: <50F007C9.10606@cn.fujitsu.com>
Date:	Fri, 11 Jan 2013 20:38:33 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	Michal Hocko <mhocko@...e.cz>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Wen Congyang <wency@...fujitsu.com>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Wu Jianguo <wujianguo@...wei.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Jiang Liu <jiang.liu@...wei.com>,
	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: mmots: memory-hotplug: implement register_page_bootmem_info_section
 of sparse-vmemmap fix

On 01/11/2013 08:12 PM, Michal Hocko wrote:
> On Fri 11-01-13 20:06:25, Tang Chen wrote:
>> On 01/11/2013 06:47 PM, Michal Hocko wrote:
>>>>
>>>> Darn! And now that I am looking at the patch closer it is too x86
>>>> centric so this cannot be in the generic code. I will try to cook
>>>> something better. Sorry about the noise.
>>>
>>> It is more complicated than I thought. One would tell it's a mess.
>>> The patch bellow fixes the compilation issue but I am not sure we want
>>> to include memory_hotplug.h into arch/x86/mm/init_64.c. Moreover
>>>
>>> +void register_page_bootmem_memmap(unsigned long section_nr,
>>> +				  struct page *start_page, unsigned long size)
>>> +{
>>> +	/* TODO */
>>> +}
>>>
>>> for other archs would suggest that the code is not ready yet. Should
>>> this rather be dropped for now?
>>
>> Hi Michal,
>>
>> Do you mean remove register_page_bootmem_memmap() from other
>> architectures ?
>
> No I meant the patch to be dropped until it gets implementation for
> other architectures or the users of the function would be explicit about
> archs which are supported. What happens if the implementation is empty
> will the generic code work properly? From my very limitted understanding
> of the code it won't.

Hi Michal,

Hum, I see. Thank you for your remind. :)
register_page_bootmem_info_section() will be different in other
architectures if register_page_bootmem_memmap() is empty.

I think we can post a patch to make register_page_bootmem_info_section()
the same as before, and we just implement the x86 version first. So that
it will have no harm to other architectures.

How do you think ?

Thanks. :)

>

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