linux-kernel - Re: [PATCH] drivers: base: new memory config sysfs driver for large memory systems

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Message-ID: <20130801205758.GB13585@kroah.com>
Date:	Fri, 2 Aug 2013 04:57:58 +0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Seth Jennings <sjenning@...ux.vnet.ibm.com>
Cc:	Nathan Fontenot <nfont@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Nivedita Singhvi <niv@...ibm.com>,
	Michael J Wolf <mjwolf@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: base: new memory config sysfs driver for large
 memory systems

On Fri, Jul 26, 2013 at 09:33:44AM -0500, Seth Jennings wrote:
> On Thu, Jul 25, 2013 at 04:38:00PM -0700, Greg Kroah-Hartman wrote:
> > On Thu, Jul 25, 2013 at 04:11:20PM -0500, Seth Jennings wrote:
> > > From: Nathan Fontenot <nfont@...ux.vnet.ibm.com>
> > > 
> > > Large memory systems (1TB or more) experience boot delays on the order
> > > of minutes due to the initializing the memory configuration part of
> > > sysfs at /sys/devices/system/memory/.
> > > 
> > > ppc64 has a memory block size of 256M and (I think) x86 is 128M.  With 1TB
> > > of RAM and a 256M block size, that's 4k memory blocks with 20 sysfs
> > > entries per block that's around 80k items that need be created at boot
> > > time in sysfs.  Some systems go up to 16TB where the issue is
> > > even more severe.
> > > 
> > > This patch is a prototype for a new sysfs memory layout where the
> > > entries are created on demand by writing memory block numbers into a
> > > "show" and "hide" files to create and destroy the memory block
> > > configuration attributes in sysfs.  This would decouple the number of
> > > sysfs entries created at boot time from the memory size, resulting in a
> > > sysfs initialization time that doesn't increase and memory size
> > > increase.
> > > 
> > > Signed-off-by: Seth Jennings <sjenning@...ux.vnet.ibm.com>
> > > Signed-off-by: Nathan Fontenot <nfont@...ux.vnet.ibm.com>
> > 
> > How does this tie into the patches Nathan sent yesterday for memory
> > hotplug stuff that I thought modified the same part of the kernel?
> 
> So this patch introduces the new layout in a new file
> drives/base/memfs.c (which, in light of your last comment should
> probably be something more like largememory.c).
> 
> It doesn't clash with Nathan's, but it doesn't contain the new
> is_memblock_[removable|offline] functions or the new "release"
> attribute.  But that can be added easily.

Can you two please work together on this so I we don't have to deal with
competing patch sets and get confused as to what is really going on
here?

thanks,

greg k-h
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