From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756701Ab1LBNwu (ORCPT ); Fri, 2 Dec 2011 08:52:50 -0500 Received: from mailhub.sw.ru ([195.214.232.25]:26567 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756566Ab1LBNwt (ORCPT ); Fri, 2 Dec 2011 08:52:49 -0500 Message-ID: <4ED8D82B.9080408@parallels.com> Date: Fri, 02 Dec 2011 17:52:43 +0400 From: Pavel Emelyanov User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc15 Thunderbird/3.1.10 MIME-Version: 1.0 To: Pedro Alves CC: KAMEZAWA Hiroyuki , Cyrill Gorcunov , "linux-kernel@vger.kernel.org" , Andrew Morton , Tejun Heo , Andrew Vagin , Serge Hallyn , Vasiliy Kulikov Subject: Re: [rfc 2/3] fs, proc: Introduce the Children: line in /proc//status References: <20111129191252.769160532@openvz.org> <201112021258.04197.pedro@codesourcery.com> <4ED8CFC4.5010804@parallels.com> <201112021344.40177.pedro@codesourcery.com> In-Reply-To: <201112021344.40177.pedro@codesourcery.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/02/2011 05:44 PM, Pedro Alves wrote: > 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? Those living in /proc//task do not live in /proc. At all. This explains everything below. > 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? Why wouldn't /proc//children work for you? This is as simple as # ls -l $(cat /proc//children) :) Thanks, Pavel