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

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Message-ID: <20130725233800.GA18349@kroah.com>
Date:	Thu, 25 Jul 2013 16:38:00 -0700
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 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?

thanks,

greg k-h
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