From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: Re: [PATCHv5 04/10] node: Link memory nodes to their compute nodes Date: Tue, 5 Feb 2019 15:52:27 +0100 Message-ID: <20190205145227.GG17950@kroah.com> References: <20190124230724.10022-1-keith.busch@intel.com> <20190124230724.10022-5-keith.busch@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J. Wysocki" Cc: Keith Busch , Linux Kernel Mailing List , ACPI Devel Maling List , Linux Memory Management List , Dave Hansen , Dan Williams List-Id: linux-acpi@vger.kernel.org On Tue, Feb 05, 2019 at 01:33:27PM +0100, Rafael J. Wysocki wrote: > > +/** > > + * struct node_access_nodes - Access class device to hold user visible > > + * relationships to other nodes. > > + * @dev: Device for this memory access class > > + * @list_node: List element in the node's access list > > + * @access: The access class rank > > + */ > > +struct node_access_nodes { > > + struct device dev; > > I'm not sure if the entire struct device is needed here. > > It looks like what you need is the kobject part of it only and you can > use a kobject directly here: > > struct kobject kobj; > > Then, you can register that under the node's kobject using > kobject_init_and_add() and you can create attr groups under a kobject > using sysfs_create_groups(), which is exactly what device_add_groups() > does. > > That would allow you to avoid allocating extra memory to hold the > entire device structure and the extra empty "power" subdirectory added > by device registration would not be there. When you use a "raw" kobject then userspace tools do not see the devices and attributes in libraries like udev. So unless userspace does not care about this at all, you should use a 'struct device' where ever possible. The memory "savings" usually just isn't worth it unless you have a _lot_ of objects being created here. Who is going to use all of this new information? thanks, greg k-h