Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751652AbaKFIOG (ORCPT ); Thu, 6 Nov 2014 03:14:06 -0500 Received: from a.ns.miles-group.at ([95.130.255.143]:65275 "EHLO radon.swed.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751096AbaKFIOB (ORCPT ); Thu, 6 Nov 2014 03:14:01 -0500 Message-ID: <545B2DC4.1090005@nod.at> Date: Thu, 06 Nov 2014 09:13:56 +0100 From: Richard Weinberger User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.0 MIME-Version: 1.0 To: "Chen, Hanxiao" , "Serge E. Hallyn" CC: "Eric W. Biederman" , Serge Hallyn , Oleg Nesterov , "containers@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" , Mateusz Guzik , David Howells Subject: Re: [PATCH 1/2v6] procfs: show hierarchy of pid namespace References: <1415184115-12022-1-git-send-email-chenhanxiao@cn.fujitsu.com> <1415184115-12022-2-git-send-email-chenhanxiao@cn.fujitsu.com> <545A13DA.3090207@nod.at> <20141105124111.GA19563@mail.hallyn.com> <545A1D53.3070507@nod.at> <5871495633F38949900D2BF2DC04883E61F2B2@G08CNEXMBPEKD02.g08.fujitsu.local> In-Reply-To: <5871495633F38949900D2BF2DC04883E61F2B2@G08CNEXMBPEKD02.g08.fujitsu.local> Content-Type: text/plain; charset=gbk Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 06.11.2014 um 06:48 schrieb Chen, Hanxiao: > > >> -----Original Message----- >> From: Richard Weinberger [mailto:richard@nod.at] >> Sent: Wednesday, November 05, 2014 8:52 PM >> To: Serge E. Hallyn >> Cc: Chen, Hanxiao/?? ????; Eric W. Biederman; Serge Hallyn; Oleg Nesterov; >> containers@lists.linux-foundation.org; linux-kernel@vger.kernel.org; Mateusz >> Guzik; David Howells >> Subject: Re: [PATCH 1/2v6] procfs: show hierarchy of pid namespace >> >> Am 05.11.2014 um 13:41 schrieb Serge E. Hallyn: >>> Quoting Richard Weinberger (richard@nod.at): >>>> Am 05.11.2014 um 11:41 schrieb Chen Hanxiao: >>>>> We lack of pid hierarchy information, and this will lead to: >>>>> a) we don't know pids' relationship, who is whose child: >>>>> /proc/PID/ns/pid only tell us whether two pids live in different ns >>>>> b) bring trouble to nested lxc container check/restore/migration >>>>> c) bring trouble to pid translation between containers; >>>>> >>>>> This patch will show the hierarchy of pid namespace >>>>> by pidns_hierarchy like: >>>>> >>>>> [root@localhost ~]#cat /proc/pidns_hierarchy >>>>> 18060 18102 1534 >>>>> 18060 18102 1600 >>>>> 1550 >>>> >>>> Hmm, what about printing the pid hierarchy in the same way as >> /proc/self/mountinfo >>>> does with mount namespaces? >>>> Your current approach is not bad but we should really try to be consistent >> with existing >>>> sources of information. >>> >>> Good point. How would you structure it to make it look mor elike mountinfo? >>> Adding the pidns inode number (in place of a mount sequence number) might be >>> useful, but it sounds like you have a more concrete idea? >> >> Just list . This way we have exactly one >> information record per line and always exactly two columns to parse. >> >> e.g. >> [root@localhost ~]#cat /proc/pidns_hierarchy >> 1550 1 >> 18060 1 >> 18102 18060 >> 1534 18102 >> 1600 18102 >> > But this style lacks of *level* information: It does not. > Ex: > 1->18060->18102->1600->1700 > If we want to check the 1700's level in pid ns > Style 1: > 18060 18102 1600 1700 > > Style 2: > 18060 1 > 18102 18060 > 1600 18102 > 1700 1600 > > If we had a little more containers, > Style 2 would not be clear enough. > 1 line vs $(PID level) line Any trivial program can find out the level of nesting. > If there were no more related information to show, > I think style 1 looks better. It is not about looking better, it is about parsing and being consistent with existing interfaces. /proc/pidns_hierarchy will be mostly read by *programs*, not humans. /proc/ has already too many horrible to parse files, please don't add another one. This is also why sysfs has the one-value-per-file rule. If it makes you feel better you can add a third column to the output which indicates the nesting level (or the distance to the initial pidns) . i.e. Style 2: 18060 1 1 18102 18060 2 1600 18102 3 1700 1600 4 Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/