Messages in this thread | | | Date | Tue, 14 Oct 2008 13:53:20 -0500 | From | "Serge E. Hallyn" <> | Subject | Re: sysfs: tagged directories not merged completely yet |
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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
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