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

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Message-Id: <20100629115232.38BC.A69D9226@jp.fujitsu.com>
Date:	Tue, 29 Jun 2010 11:56:18 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	kosaki.motohiro@...fujitsu.com, Greg KH <gregkh@...e.de>,
	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 Mon, 2010-06-28 at 08:44 -0700, Greg KH wrote:
> > > The directories being created are the standard directories, one for each of the memory
> > > sections present at boot.  I think the most used files in each of these directories
> > > is the state and removable file used to do memory hotplug.
> > 
> > And perhaps we shouldn't really be creating so many directories?  Why
> > not work with the memory hotplug developers to change their interface to
> > not abuse sysfs in such a manner? 
> 
> Heh, it wasn't abuse until we got this much memory.  But, I think this
> one is pretty much 100% my fault.
> 
> Nathan, I think the right fix here is probably to untie sysfs from the
> sections a bit.  We should be able to have sysfs dirs that represent
> more than one contiguous SECTION_SIZE area of memory.

Why do we need abi breakage? Yourself talked about we guess ppc don't
actually need 16MB section. I think IBM folks have to confirm it.
If our guessing is correct, the firmware fixing is only necessary.

Thats said, I don't 100% refuse your idea. it's interesting. but, 
In generical I hate _unncessary_ abi change.


> It will mean re-teaching some of the tools how things work.  They'll
> have to know that you can split mem sections, and we'll have to come up
> with a way to do the splitting.  
> 
> Does ppc *really* remove 16MB sections of RAM these days?  It's probably
> worth checking with the firmware folks to see what the limits are in
> practice.
> 
> -- Dave
> 



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