linux-kernel - Re: [PATCH] memory hotplug disable boot option

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Date:	Thu, 01 Jul 2010 06:23:15 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Greg KH <gregkh@...e.de>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Nathan Fontenot <nfont@...tin.ibm.com>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH] memory hotplug disable boot option

On Thu, 2010-07-01 at 09:31 +0900, KAMEZAWA Hiroyuki wrote:
> 
> Considering briefly, how about this compact layout ?
> 
> /sys/devices/system/memory/:
>                             list, hide, show, memoryX...
> 
> list: // show available memory index list.
>   #cat list
>    0 1 2 ....10000...
> 
> show: //an interface to enable the interface.
>   #echo INDEX > memory_index
>   will create memoryINDEX diretory.
> 
> hide: //an interface to hide the interface.
>   #echo INDEX > memory_hide
>   will remove memoryINDEX sysfs directory.

I was thinking more along the lines of just taking adjacent sections and
merging them.  We'll need a new "end address" or size file.  Maybe
"end_phys_index" or something similar.

Such a beast would not fix all of the pathological cases, like where
only every other 16MB section is populated with RAM, but I don't think
those are very common at all, especially in cases where there's a lot of
RAM.  But, it also has a chance of being relatively backward-compatible.
In most cases, we may even be able to calculate a new phys_block_size
where everything fits evenly and be fully backward-compatible with the
old ABI.

-- Dave

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