From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx103.postini.com [74.125.245.103]) by kanga.kvack.org (Postfix) with SMTP id 3EEB06B0032 for ; Wed, 14 Aug 2013 15:43:50 -0400 (EDT) Date: Wed, 14 Aug 2013 12:43:48 -0700 From: Greg Kroah-Hartman Subject: Re: [RFC][PATCH] drivers: base: dynamic memory block creation Message-ID: <20130814194348.GB10469@kroah.com> References: <1376508705-3188-1-git-send-email-sjenning@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1376508705-3188-1-git-send-email-sjenning@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Seth Jennings Cc: Dave Hansen , Nathan Fontenot , Cody P Schafer , Andrew Morton , Lai Jiangshan , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Wed, Aug 14, 2013 at 02:31:45PM -0500, Seth Jennings wrote: > 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/. Are you sure that is the problem area? Have you run perf on it? > ppc64 has a normal memory block size of 256M (however sometimes as low > as 16M depending on the system LMB size), 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. The x86 developers are working with larger memory sizes and they haven't seen the problem in this area, for them it's in other places, as I referred to in my other email. > This patch provides a means by which users can prevent the creation of > the memory block attributes at boot time, yet still dynamically create > them if they are needed. > > This patch creates a new boot parameter, "largememory" that will prevent > memory_dev_init() from creating all of the memory block sysfs attributes > at boot time. Instead, a new root attribute "show" will allow > the dynamic creation of the memory block devices. > Another new root attribute "present" shows the memory blocks present in > the system; the valid inputs for the "show" attribute. You never documented any of these abi changes, which is a requirement (not that I'm agreeing that a boot parameter is ok...) > There was a significant amount of refactoring to allow for this but > IMHO, the code is much easier to understand now. Care to refactor things first, with no logical changes, and then make your changes in a follow-on patch, so that people can actually find what you changed in the patch? Remember, a series of patches please, not one big "refactor and change it all" patch. thanks, greg k-h -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org