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

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Date:	Thu, 1 Jul 2010 16:26:34 -0700
From:	Greg KH <gregkh@...e.de>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Dave Hansen <dave@...ux.vnet.ibm.com>,
	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, Jul 01, 2010 at 09:31:30AM +0900, KAMEZAWA Hiroyuki wrote:
> On Wed, 30 Jun 2010 08:47:55 -0700
> Greg KH <gregkh@...e.de> wrote:
> > > and adding a scalable interface for large scale machines ?
> > > I'd like to consider something..
> > 
> > Dynamically changing the layout on big memory boxes makes sense to me,
> > how about you?
> > 
> 
> like this ?
> ==
> boot option:
> memory_sysfs_layout=compact
> memory_sysfs_layout=auto (default)
> memory_sysfs_layout=full
> 
> 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.

Ick, that can get confusing very quickly, and not really solve any of
your root problems, right?

> In compact mode, all memoryX interface are hidden at boot.
> In full mode, all memoryX interaface are shown.
> The Boot option just affects status at boot. If users want, he can make
> all memory sysfs in shown state.
> 
> At hot-add event (via acpi) or probe-event, newly created memory section
> should be start from "shown" mode. hotplug scirpt can hide it after online.
> 
> At hot-remove, the users has to offline memory before hotplug. He'll has
> to do check list and show interface.
> 
> I think this change is not very difficult technically but can this kind of
> interface be allowed ?

Not really, I don't like it.

Why not just simplify what you currently have to not use so many
directories and files?

And maybe, this doesn't belong in sysfs at all...

thanks,

greg k-h
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