Date: Wed, 30 Jun 2010 08:47:55 -0700
From: Greg KH <gregkh@suse.de>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Nathan Fontenot <nfont@austin.ibm.com>,
       Andi Kleen <andi@firstfloor.org>, linux-kernel@vger.kernel.org,
       "Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: [PATCH] memory hotplug disable boot option
Message-ID: <20100630154755.GB12158@suse.de>
References: <20100628154455.GA13918@suse.de>
 <1277769867.8354.531.camel@nimitz>
 <20100629115232.38BC.A69D9226@jp.fujitsu.com>
 <1277827384.8354.3413.camel@nimitz>
 <20100629180415.GB1240@suse.de>
 <20100630093251.a30ed1e0.kamezawa.hiroyu@jp.fujitsu.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20100630093251.a30ed1e0.kamezawa.hiroyu@jp.fujitsu.com>
User-Agent: Mutt/1.5.20 (2009-06-14)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2477
Lines: 60

On Wed, Jun 30, 2010 at 09:32:51AM +0900, KAMEZAWA Hiroyuki wrote:
> On Tue, 29 Jun 2010 11:04:15 -0700
> Greg KH <gregkh@suse.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

It will not be "NEW" in a year :)

>  memory_sysfs_layout=small boot option

Yes, that sounds good.

> 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?

thanks,

greg k-h
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/