Messages in this thread | | | Subject | Re: (pspace,pid) vs true pid virtualization | From | (Eric W. Biederman) | Date | Fri, 17 Feb 2006 05:16:06 -0700 |
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Herbert Poetzl <herbert@13thfloor.at> writes:
> On Fri, Feb 17, 2006 at 03:57:26AM -0700, Eric W. Biederman wrote: >> As for that. When I mad that suggestion to Herbert Poetzl >> his only concern was that a smart init might be too heavy weight >> for lightweight vserver. Generally I like the idea. > > well, may I remind that this solution would require _two_ > init processes for each guest, which could easily make up > 300-400 unnecessary processes in a lightweight server > setup?
I take it seriously enough that I remembered the concern, and I think it is legitimate. Figuring out how to safely set the policy is a challenge. That is something a user space daemon trivially gets right.
The kernel side of a process is about 10K if the user space side was also lightweight we could have the entire per process cost in the 30K range. 30K*400 = 12000K = 12M.
That is significant but we are still cheap enough that it isn't necessarily a show stopper.
I think the cost was only one extra process, for the case where you have fakeinit now it would be init, for other cases it would be a daemon that gets setup when you initialize the vserver.
If we can get a permission checking model in the kernel right it is potentially much cheaper, to have an enter model.
Having user space as a backup to that is still interesting.
>> > (Read the last sentence, and in case you're wondering, no I don't have >> > any children in real life) >> >> Speaking of that. One of my coworkers mentioned that it is unfortunate >> that our names don't have the double meaning. So it was suggested we >> call them >> >> Speaking of that problematic naming. One of my coworkers mentioned that >> it is unfortunate that our set of names does not have a double meaning. >> After that the suggestion came up to call them families, instead of guest >> or pidspaces. Although I guess calling them guests is about as bad :) > > well, at least Guests or VEs are terms already used by > existing projects, where pspace sounds somewhat strange. > > at the same time I'd like to point out that *spaces is > a good name for the building blocks, but we definitely > have to name the 'construct' different, i.e. a 'guest' > (or VPS or VE or whatever) is _more_ than just a p-space > it's the sum of all *-spaces required to make it look > like a real linux system.
I totally agree. Sorry. This was meant as a humerous tangent! I thought the smiley and the fact I was looking for a name with a double meaning that would have made it easier to get confused would have made that clear!
Oh well such is confusion an email :)
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