From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756277AbaE2KCs (ORCPT ); Thu, 29 May 2014 06:02:48 -0400 Received: from relay.parallels.com ([195.214.232.42]:50101 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750725AbaE2KCr (ORCPT ); Thu, 29 May 2014 06:02:47 -0400 Message-ID: <5387059E.9010105@parallels.com> Date: Thu, 29 May 2014 14:02:06 +0400 From: Pavel Emelyanov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 MIME-Version: 1.0 To: Richard Weinberger CC: Vasily Kulikov , , Serge Hallyn , , Oleg Nesterov , David Howells , "Eric W. Biederman" , Andrew Morton , Al Viro Subject: Re: [PATCH v2] /proc/pid/status: show all sets of pid according to ns References: <1401272683-1659-1-git-send-email-chenhanxiao@cn.fujitsu.com> <5385DA19.2060008@parallels.com> <20140528182824.GA5057@cachalot> <53863889.9080509@parallels.com> <20140529055954.GA10354@cachalot> <5386F8EA.8050501@parallels.com> <5386FC0C.9000307@nod.at> <538700B5.5070601@parallels.com> <538703D0.7030308@nod.at> In-Reply-To: <538703D0.7030308@nod.at> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.24.36.87] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/29/2014 01:54 PM, Richard Weinberger wrote: > Am 29.05.2014 11:41, schrieb Pavel Emelyanov: >> On 05/29/2014 01:21 PM, Richard Weinberger wrote: >>> Am 29.05.2014 11:07, schrieb Pavel Emelyanov: >>>> On 05/29/2014 09:59 AM, Vasily Kulikov wrote: >>>>> On Wed, May 28, 2014 at 23:27 +0400, Pavel Emelyanov wrote: >>>>>> On 05/28/2014 10:28 PM, Vasily Kulikov wrote: >>>>>>> On Wed, May 28, 2014 at 16:44 +0400, Pavel Emelyanov wrote: >>>>>>> It will be simplier >>>>>>> to parse the file -- if 'ns_ids' file contains some ID then this ID for >>>>>>> every ns can be obtained regardless of the specific ID name (SID, PID, >>>>>>> PGID, etc.). >>>>>> >>>>>> True, but given a task PID how to determine which pid namespaces it lives in >>>>>> to get the idea of how PIDs map to each other? Maybe we need some explicit >>>>>> API for converting (ID, NS1, NS2) into (ID)? >>>>> >>>>> AFAIU the idea of the patch is to add a new debugging information which >>>>> can be trivially obtained via 'cat /proc/...': >>>> >>>> I agree, but this ability will be very useful by checkpoint-restore project >>>> too and I'd really appreciate if the API we have for that would be scalable >>>> enough. Per-task proc file works for me, but how about sid-s and pgid-s? >>> >>> What kind of information does CRIU need? >> >> We need to know what pid namespaces a task lives in and how pid, sid and >> pgid look in all of them. A short example with pids only > > So use case is to checkpoint/restore nested containers? :) Yes, but there's one more scenario. AFAIK some applications create pid namespaces themselves, without starting what is typically called "a container" :) And when such an applications are run inside, well ... "more real" container (e.g. using openvz, lxc or docker tools) we face this issue. Thanks, Pavel