Subject: Re: [PATCH] memory hotplug disable boot option
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Greg KH <gregkh@suse.de>, Nathan Fontenot <nfont@austin.ibm.com>,
       Andi Kleen <andi@firstfloor.org>, linux-kernel@vger.kernel.org,
       "Eric W. Biederman" <ebiederm@xmission.com>
In-Reply-To: <20100629115232.38BC.A69D9226@jp.fujitsu.com>
References: <20100628154455.GA13918@suse.de>
	 <1277769867.8354.531.camel@nimitz>
	 <20100629115232.38BC.A69D9226@jp.fujitsu.com>
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Date: Tue, 29 Jun 2010 09:03:04 -0700
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On Tue, 2010-06-29 at 11:56 +0900, KOSAKI Motohiro wrote:
> > 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.

>From the mouth of the kernel dumbass who coded this up: it's not the
firmware's fault.  We shouldn't punt this to them, and the proper fix
_isn't_ in the firmware, plus they may have other more fundamental
reasons to keep the LMB sizes what they are.

-- Dave

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