From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with ESMTP id 3767D8D000E for ; Wed, 1 Dec 2010 20:26:21 -0500 (EST) Received: from hpaq12.eem.corp.google.com (hpaq12.eem.corp.google.com [172.25.149.12]) by smtp-out.google.com with ESMTP id oB21LrSX017077 for ; Wed, 1 Dec 2010 17:21:53 -0800 Received: from pxi17 (pxi17.prod.google.com [10.243.27.17]) by hpaq12.eem.corp.google.com with ESMTP id oB21Lp98021976 for ; Wed, 1 Dec 2010 17:21:51 -0800 Received: by pxi17 with SMTP id 17so1473021pxi.20 for ; Wed, 01 Dec 2010 17:21:50 -0800 (PST) Date: Wed, 1 Dec 2010 17:21:48 -0800 (PST) From: David Rientjes Subject: Re: [8/8, v6] NUMA Hotplug Emulator: implement debugfs interface for memory probe In-Reply-To: <20101201234514.GA13509@shaohui> Message-ID: References: <20101130071324.908098411@intel.com> <20101130071437.461969179@intel.com> <20101201234514.GA13509@shaohui> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Shaohui Zheng Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, lethal@linux-sh.org, Andi Kleen , dave@linux.vnet.ibm.com, Greg KH , Haicheng Li List-ID: On Thu, 2 Dec 2010, Shaohui Zheng wrote: > > > From: Shaohui Zheng > > > > > > Implement a debugfs inteface /sys/kernel/debug/mem_hotplug/probe for meomory hotplug > > > emulation. it accepts the same parameters like > > > /sys/devices/system/memory/probe. > > > > > > > NACK, we don't need two interfaces to do the same thing. > > You may not know the background, the sysfs memory/probe interface is a general > interface. Even through we have a debugfs interface, we should still keep it. > > For test purpose, the sysfs is enough, according to the comments from Greg & Dave, > we create the debugfs interface. > I doubt either Greg or Dave suggested adding duplicate interfaces for the same functionality. The difference is that we needed to add the add_node interface in a new mem_hotplug debugfs directory because it's only useful for debugging kernel code and, thus, doesn't really have an appropriate place in sysfs. Nobody is going to use add_node unless they lack hotpluggable memory sections in their SRAT and want to debug the memory hotplug callers. For example, I already wrote all of this node hotplug emulation stuff when I wrote the node hotplug support for SLAB. Memory hotplug, however, does serve a non-debugging function and is appropriate in sysfs since this is how people hotplug memory. It's an ABI that we can't simply remove without deprecation over a substantial period of time and in this case it doesn't seem to have a clear advantage. We need not add special emulation support for something that is already possible for real systems, so adding a duplicate interface in debugfs is inappropriate. -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org