Re: What can OpenVZ do?

From: Ingo Molnar
Date: Wed Feb 18 2009 - 18:16:37 EST



* Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> wrote:

> On Wed, 2009-02-18 at 19:16 +0100, Ingo Molnar wrote:
> > Nothing motivates more than app designers complaining about the
> > one-way flag.
> >
> > Furthermore, it's _far_ easier to make a one-way flag SMP-safe.
> > We just set it and that's it. When we unset it, what do we about
> > SMP races with other threads in the same MM installing another
> > non-linear vma, etc.
>
> After looking at this for file descriptors, I have to really
> agree with Ingo on this one, at least as far as the flag is
> concerned. I want to propose one teeny change, though: I
> think the flag should be per-resource.
>
> We should have one flag in mm_struct, one in files_struct,
> etc... The task_is_checkpointable() function can just query
> task->mm, task->files, etc... This gives us nice behavior at
> clone() *and* fork that just works.
>
> I'll do this for files_struct and see how it comes out so you
> can take a peek.

Yeah, per resource it should be. That's per task in the normal
case - except for threaded workloads where it's shared by
threads.

Ingo
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