From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756676Ab1LBNoq (ORCPT ); Fri, 2 Dec 2011 08:44:46 -0500 Received: from relay1.mentorg.com ([192.94.38.131]:36210 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755618Ab1LBNop (ORCPT ); Fri, 2 Dec 2011 08:44:45 -0500 From: Pedro Alves Organization: CodeSourcery To: Pavel Emelyanov Subject: Re: [rfc 2/3] fs, proc: Introduce the Children: line in /proc//status Date: Fri, 2 Dec 2011 13:44:39 +0000 User-Agent: KMail/1.13.6 (Linux/2.6.38-13-generic; KDE/4.7.2; x86_64; ; ) Cc: KAMEZAWA Hiroyuki , Cyrill Gorcunov , "linux-kernel@vger.kernel.org" , Andrew Morton , Tejun Heo , Andrew Vagin , Serge Hallyn , Vasiliy Kulikov References: <20111129191252.769160532@openvz.org> <201112021258.04197.pedro@codesourcery.com> <4ED8CFC4.5010804@parallels.com> In-Reply-To: <4ED8CFC4.5010804@parallels.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201112021344.40177.pedro@codesourcery.com> X-OriginalArrivalTime: 02 Dec 2011 13:44:43.0059 (UTC) FILETIME=[8BCA9830:01CCB0F8] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday 02 December 2011 13:16:52, Pavel Emelyanov wrote: > On 12/02/2011 04:58 PM, Pedro Alves wrote: > > On Friday 02 December 2011 12:43:10, Pavel Emelyanov wrote: > > > >>>> Yes, I like /children file. other points seems to be pointed out by other > >>>> reviewers. > >>> > >>> Any reason this is a file instead of a directory like /proc/PID/task/ ? > >>> > >>> $ sudo ls /proc/8167/task/ > >>> 8167 854 855 856 857 858 859 > >>> $ sudo ls /proc/8167/task/855/ > >>> attr clear_refs cpuset exe io loginuid mountinfo oom_adj pagemap sched smaps statm wchan > >>> auxv cmdline cwd fd latency maps mounts oom_score personality schedstat stack status > >>> cgroup comm environ fdinfo limits mem numa_maps oom_score_adj root sessionid stat syscall > >>> > >>> Much easier to follow the chain from the command line this way. > >> > >> What do you propose to put into these directories? Another directories named with > >> children pid-s? > > > > Yes, just like the task/ dir gives you directories named with the > > processes's thread ids. Opening /proc/PID/children/PID-CHILD1/ would get > > you the same as opening /proc/PID-CHILD1/. Just like > > opening /proc/PID/task/PID-CHILD1/ gets you (almost) the same as opening > > /proc/PID-CHILD1/. > > You cannot make the dentry named /proc//children/ be a hardlink on > the /proc/. Thus you have to make arbitrary amount of inodes to point to > a single task. This brings unnecessary complexity and memory usage (by dentries > and proc inodes). How is this different from the _already existing_ /proc//task/ directory? I can imagine that 98% of the code would be shared even? It's "just" a matter of listing thread group children (child/), instead of clone children (task/), isn't it? They are not symbolic links under task/. /proc//task// does not have a task/ subdir, only /proc// does, I guess to avoid the memory usage issue you raise. > I'd accept the symbolic links, but how would they look like? Like this: > # ls -l /proc/123/children > 234 -> ../../234 > ? That'd work for me... but really, why not reuse tasks/'s code and behave the same? -- Pedro Alves