From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757934AbZE0Wk5 (ORCPT ); Wed, 27 May 2009 18:40:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758325AbZE0Wkm (ORCPT ); Wed, 27 May 2009 18:40:42 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:42567 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757461AbZE0Wkl (ORCPT ); Wed, 27 May 2009 18:40:41 -0400 Date: Wed, 27 May 2009 15:40:01 -0700 From: Andrew Morton To: Alexey Dobriyan Cc: orenl@cs.columbia.edu, serge@hallyn.com, linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, xemul@parallels.com Subject: Re: [PATCH 18/38] C/R: core stuff Message-Id: <20090527154001.86a5abff.akpm@linux-foundation.org> In-Reply-To: <20090527221753.GB8321@x200.localdomain> References: <1242968132-1044-1-git-send-email-adobriyan@gmail.com> <1242968132-1044-18-git-send-email-adobriyan@gmail.com> <20090526131644.GA20920@hallyn.com> <20090526193503.GB11909@x200.localdomain> <4A1DA8FB.3000306@cs.columbia.edu> <20090527221753.GB8321@x200.localdomain> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.20; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 28 May 2009 02:17:53 +0400 Alexey Dobriyan wrote: > > 1) Whether or not allow c/r of sub-container (partial hierarchy) > > > > 2) Creation of restarting process hierarchy in kernel or in userspace > > > > As for #1, you are the _only_ one who advocates restricting c/r to > > a full container only. I guess you have your reasons, but I'm unsure > > what they may be. > > The reason is that checkpointing half-frozen, half-live container is > essentially equivalent to live container which adds much complexity > to code fundamentally preventing kernel from taking coherent snapshot. > > In such situations kernel will do its job badly. > > Manpage will be filled with strings like "if $FOO is shared then $BAR is > not guaranteed". > > What to do if user simply doesn't know if container is bounded? > Checkpoint and to hell with consequences? > > If two tasks share mm_struct you can't even detect that pages you dump > aren't filled with garbage meanwhile from second task. > > If two tasks share mm_struct, other task can issue AIO indefinitely > preventing from taking even coherent filesystem snapshot. > > That's why I raise this issue again to hear from people what they think > and these people shouldn't be containers and C/R people, because the > latter already made up their minds. > > This is super-important issue to get right from the beginning. yeah, checkpointing a partial hierarchy at this stage sounds like overreach. Get full-container working usably first, think about sub-containers in version 2.