Messages in this thread | | | Date | Mon, 20 Feb 2006 12:17:39 +0300 | From | Kirill Korotaev <> | Subject | Re: (pspace,pid) vs true pid virtualization |
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>> However, if we're going to get anywhere, the first decision which we >> need to make is whether to go with a (container,pid), (pspace,pid) or >> equivalent pair like approach, or a virtualized pid approach. Linus had >> previously said that he prefers the former. Since there has been much >> discussion since then, I thought I'd try to recap the pros and cons of >> each approach, with the hope that the head Penguins will chime in one >> more time, after which we can hopefully focus our efforts. I think the first thing we have to do, is not to decide which pids we want to see, but what and how we want to virtualize.
> I am thinking that you can have both. Not in the sense of > overcomplicating, but in the sense of having your cake and eating it > too. BTW, really, why not both? Eric, can we do something universal which will suite all the parties?
> The only thing which is a unique, system wide identifier for the process > is the &task_struct. So we are already virtualising this pointer into a > PID for userland. The only difference is that we cache it (nay, keep > the authorative version of it) in the task_struct. > > The (XID, PID) approach internally is also fine. This says that there > is a container XID, and within it, the PID refers to a particular > task_struct. A given task_struct will likely exist in more than one > place in the (XID, PID) space. Perhaps the values of PID for XID = 0 > and XID = task.xid can be cached in the task_struct, but that is a > detail. > > Depending on the flags on the XID, we can incorporate all the approaches > being tabled. You want virtualised pids? Well, that'll hurt a little, > but suit yourself - set a flag on your container and inside the > container you get virtualised PIDs. You want a flat view for all your > vservers? Fine, just use an XID without the virtualisation flag and > with the "all seeing eye" property set. Or you use an XID _with_ the > virtualisation flag set, and then call a tuple-endowed API to find the > information you're after. This sounds good. But pspaces are also used for access controls. So this should be incorparated there as well.
Kirill
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