Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757587Ab3HNXut (ORCPT ); Wed, 14 Aug 2013 19:50:49 -0400 Received: from hydra.sisk.pl ([212.160.235.94]:43214 "EHLO hydra.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750861Ab3HNXur (ORCPT ); Wed, 14 Aug 2013 19:50:47 -0400 From: "Rafael J. Wysocki" To: Seth Jennings Cc: Greg Kroah-Hartman , Dave Hansen , Nathan Fontenot , Cody P Schafer , Andrew Morton , Lai Jiangshan , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC][PATCH] drivers: base: dynamic memory block creation Date: Thu, 15 Aug 2013 02:01:09 +0200 Message-ID: <5959614.447qgH8r7c@vostro.rjw.lan> User-Agent: KMail/4.9.5 (Linux/3.11.0-rc5+; KDE/4.9.5; x86_64; ; ) In-Reply-To: <1376508705-3188-1-git-send-email-sjenning@linux.vnet.ibm.com> References: <1376508705-3188-1-git-send-email-sjenning@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1884 Lines: 40 On Wednesday, August 14, 2013 02:31:45 PM 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/. > > 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. > > 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. I wonder how this is going to work with the ACPI device object binding to memory blocks that's in 3.11-rc. That stuff will only work if the memory blocks are already there when acpi_memory_enable_device() runs and that is called from the ACPI namespace scanning code executed (1) during boot and (2) during hotplug. So I don't think you can just create them on the fly at run time as a result of a sysfs write. Thanks, Rafael -- 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/