From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752844AbZBZSah (ORCPT ); Thu, 26 Feb 2009 13:30:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751900AbZBZSa1 (ORCPT ); Thu, 26 Feb 2009 13:30:27 -0500 Received: from mtagate2.de.ibm.com ([195.212.17.162]:36113 "EHLO mtagate2.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751819AbZBZSa0 (ORCPT ); Thu, 26 Feb 2009 13:30:26 -0500 Subject: Re: How much of a mess does OpenVZ make? ;) Was: What can OpenVZ do? From: Greg Kurz To: Ingo Molnar Cc: Alexey Dobriyan , linux-api@vger.kernel.org, containers@lists.linux-foundation.org, hpa@zytor.com, linux-kernel@vger.kernel.org, Dave Hansen , linux-mm@kvack.org, viro@zeniv.linux.org.uk, mpm@selenic.com, Andrew Morton , torvalds@linux-foundation.org, tglx@linutronix.de, xemul@openvz.org In-Reply-To: <20090226173302.GB29439@elte.hu> References: <1233076092-8660-1-git-send-email-orenl@cs.columbia.edu> <1234285547.30155.6.camel@nimitz> <20090211141434.dfa1d079.akpm@linux-foundation.org> <1234462282.30155.171.camel@nimitz> <1234467035.3243.538.camel@calx> <20090212114207.e1c2de82.akpm@linux-foundation.org> <1234475483.30155.194.camel@nimitz> <20090212141014.2cd3d54d.akpm@linux-foundation.org> <1234479845.30155.220.camel@nimitz> <20090226162755.GB1456@x200.localdomain> <20090226173302.GB29439@elte.hu> Content-Type: text/plain Date: Thu, 26 Feb 2009 19:30:16 +0100 Message-Id: <1235673016.5877.62.camel@bahia> Mime-Version: 1.0 X-Mailer: Evolution 2.24.4 (2.24.4-1.fc10) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2009-02-26 at 18:33 +0100, Ingo Molnar wrote: > I think the main question is: will we ever find ourselves in the > future saying that "C/R sucks, nobody but a small minority uses > it, wish we had never merged it"? I think the likelyhood of that > is very low. I think the current OpenVZ stuff already looks very We've been maintaining for some years now a C/R middleware with only a few hooks in the kernel. Our strategy is to leverage existing kernel paths as they do most of the work right. Most of the checkpoint is performed from userspace, using regular syscalls in a signal handler or /proc parsing. Restart is a bit trickier and needs some kernel support to bypass syscall checks and enforce a specific id for a resource. At the end, we support C/R and live migration of networking apps (websphere application server for example). >>From our experience, we can tell: Pros: mostly not-so-tricky userland code, independent from kernel internals Cons: sub-optimal for some resources -- Gregory Kurz gkurz@fr.ibm.com Software Engineer @ IBM/Meiosys http://www.ibm.com Tel +33 (0)534 638 479 Fax +33 (0)561 400 420 "Anarchy is about taking complete responsibility for yourself." Alan Moore.