Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753929AbYJNSxh (ORCPT ); Tue, 14 Oct 2008 14:53:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751859AbYJNSxa (ORCPT ); Tue, 14 Oct 2008 14:53:30 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:52855 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751634AbYJNSx3 (ORCPT ); Tue, 14 Oct 2008 14:53:29 -0400 Date: Tue, 14 Oct 2008 13:53:20 -0500 From: "Serge E. Hallyn" To: Tejun Heo Cc: "Eric W. Biederman" , Greg KH , Al Viro , Benjamin Thery , linux-kernel@vger.kernel.org, Al Viro , Linus Torvalds Subject: Re: sysfs: tagged directories not merged completely yet Message-ID: <20081014185320.GA24908@us.ibm.com> References: <20080922153455.GA6238@kroah.com> <48D8FC1E.6000601@bull.net> <20081003101331.GH28946@ZenIV.linux.org.uk> <20081005053236.GA9472@kroah.com> <20081007222726.GA9465@kroah.com> <48EBF21E.40709@kernel.org> <48F45075.7000003@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <48F45075.7000003@kernel.org> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3577 Lines: 80 Quoting Tejun Heo (tj@kernel.org): > >> Can somebody hammer the big picture regarding namespaces into my > >> small head? > > > > 100,000 foot view. A namespace introduces a scope so multiple > > objects can have the same name. Like network devices. > > > > 10,000 foot view. The network namespace looks to user space > > as if the kernel has multiple independent network stacks. > > > > 1000 foot view. I have two network devices named lo, and sysfs > > does not currently have a place for me to put them. > > > > Leakage and being able to fool an application that it has the entire > > kernel to itself are not concerns. The goal is simply to get the > > entire object name to object translation boundary and the namespace > > work is done. We have largely achieved, and the code to do > > so once complete is reasonable enough that it should be no > > worse than dealing with any other kernel bug. > > Yes, I'm aware of the goals. What I'm curious about is the consensus > regarding network namespace and all its implications. It adds a lot > of complexities over a lot of places. e.g. following the sysfs code > becomes quite a bit more difficult after the namespace changes (maybe > it's just me but still). So, I was asking whether people generally > agree that having the namespace thing is worth the added complexities. > > I think it serves pretty small group of users. Hosting service I don't think that's true. Let's say i want to run debootstrap and set up a minimal image to run postfix. Now if I want to run that on my laptop as its own minimal separate machine, I need to run qemu or kvm. That's huge. Once we finally get network namespaces(-sysfs) finished, I can set up a 10-line config file, download and install https://sourceforge.net/projects/lxc/, run lxc-execute -n postfix-cont /bin/bash and voila, I have postfix running as though on a separate machine, but with none of the kvm/qemu overhead. Which means that instead of being able to do one at a time, i can do... hundreds? So I think this is something everyone will find useful - but of course I *am* biased :) > providers and people trying to migrate processes from one machine to > another, both of which can be served pretty well with virtualization. > It does have higher overhead both processing power and memory wise but > IIUC the former is being actively worked on w/ new processor features > like nested paging tables and all and memory is really cheap these > days, so I'm a bit skeptical how much this is needed and how much we > should pay for it. > > Another venue to explore is whether the partial view of proc and sysfs > can be implemented in less pervasive way. Implementing it via FUSE > might not be easier per-se but I think it would be better to do it Again fuse doesn't address the *core* issue (sysfs needing a way to create files for multiple devicenames with same name). But I believe Benjamin was looking into a minimal patch to fix that. Benjamin, have you gotten anywhere with that? > that way if we can instead of adding complexities to both proc and > sysfs. > > One last thing that came to mind is, how would uevents be handled? > ie. what happens if a network card which is presented as ethN in the > namespace goes away? How does the system deal with it? > > Thanks. > > -- > tejun -- 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/