From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161075AbXCGAwK (ORCPT ); Tue, 6 Mar 2007 19:52:10 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161070AbXCGAwK (ORCPT ); Tue, 6 Mar 2007 19:52:10 -0500 Received: from smtp.osdl.org ([65.172.181.24]:40308 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161075AbXCGAwJ (ORCPT ); Tue, 6 Mar 2007 19:52:09 -0500 Date: Tue, 6 Mar 2007 16:51:50 -0800 (PST) From: Linus Torvalds To: Davide Libenzi cc: Avi Kivity , Linux Kernel Mailing List , Andrew Morton , Al Viro Subject: Re: [patch] epoll use a single inode ... In-Reply-To: Message-ID: References: <45ED1A3C.6030707@argo.co.il> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org [ Al Viro added to Cc: as the arbiter of good taste in the VFS layer. He has veto powers even over my proposals ;^] On Tue, 6 Mar 2007, Davide Libenzi wrote: > > I currently have the dentry to carry the name of the file* class it is > linked to. I'd prefer to keep it that way, unless there are huge factors > against. I assume that the *only* reason for having multiple dentries is really just the output in /proc//fd/, right? Or is there any other reason to have separate dentries for these pseudo-files? It's a bit sad to waste that much memory (and time) on something like that. I bet that the dentry setup is a noticeable part of the whole sigfd()/timerfd() setup. It's likely also a big part of any memory footprint if you have lots of them. So how about just doing: - do a single dentry - make a "struct file_operations" member function that prints out the name of the thing in /proc//fd/, and which *defaults* to just doing the d_path() on the dentry, but special filesystems like this could do something else (like print out a fake inode number from the "file->f_private_data" information) There seems to really be no downsides to that approach. No existing filesystem will even notice (they'll all have NULL in the new f_op member), and it would allow pipes etc to be sped up and use less memory. Linus