* Alexey Dobriyan <adobriyan@xxxxxxxxx> wrote: > On Fri, Mar 13, 2009 at 02:01:50PM -0700, Linus Torvalds wrote: > > > > > > On Fri, 13 Mar 2009, Alexey Dobriyan wrote: > > > > > > > > Let's face it, we're not going to _ever_ checkpoint any > > > > kind of general case process. Just TCP makes that > > > > fundamentally impossible in the general case, and there > > > > are lots and lots of other cases too (just something as > > > > totally _trivial_ as all the files in the filesystem > > > > that don't get rolled back). > > > > > > What do you mean here? Unlinked files? > > > > Or modified files, or anything else. "External state" is a > > pretty damn wide net. It's not just TCP sequence numbers and > > another machine. > > I think (I think) you're seriously underestimating what's > doable with kernel C/R and what's already done. > > I was told (haven't seen it myself) that Oracle installations > and Counter Strike servers were moved between boxes just fine. > > They were run in specially prepared environment of course, but > still. That's the kind of stuff i'd like to see happen. Right now the main 'enterprise' approach to do migration/consolidation of server contexts is based on hardware virtualization - but that pushes runtime overhead to the native kernel and slows down the guest context as well - massively so. Before we've blinked twice it will be a 'required' enterprise feature and enterprise people will measure/benchmark Linux server performance in guest context primarily and we'll have a deep performance pit to dig ourselves out of. We can ignore that trend as uninteresting (it is uninteresting in a number of ways because it is partly driven by stupidity), or we can do something about it while still advancing the kernel. With containers+checkpointing the code is a lot scarier (we basically do system call virtualization), the environment interactions are a lot wider and thus they are a lot more difficult to handle - but it's all a lot faster as well, and conceptually so. All the runtime overhead is pushed to the checkpointing step - (with some minimal amount of data structure isolation overhead). I see three conceptual levels of virtualization: - hardware based virtualization, for 'unaware OSs' - system call based virtualization, for 'unaware software' - no virtualization kernel help is needed _at all_ to checkpoint 'aware' software. We have libraries to checkpoint 'aware' user-space just fine - and had them for a decade. Ingo _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
