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

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Message-Id: <20100630093251.a30ed1e0.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Wed, 30 Jun 2010 09:32:51 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Greg KH <gregkh@...e.de>
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 Tue, 29 Jun 2010 11:04:15 -0700
Greg KH <gregkh@...e.de> wrote:

> On Tue, Jun 29, 2010 at 09:03:04AM -0700, Dave Hansen wrote:
> > 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.
> 
> I agree, this should be fixed in the api to userspace, having this many
> sysfs directories and/or files is just looney.
> 
> thanks,
> 

Hmm, adding 
 CONFIG_NEW_MEMORY_SYSFS_LAYOUT or
 memory_sysfs_layout=small boot option
and adding a scalable interface for large scale machines ?
I'd like to consider something..

Thanks,
-Kame



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