[Xen-devel] Re: Interaction between Xen and XFS: stray RW mappings

[dean gaudet <dean@xxxxxxxxxx>]

On Sun, 21 Oct 2007, Jeremy Fitzhardinge wrote:

> dean gaudet wrote:
> > On Mon, 15 Oct 2007, Nick Piggin wrote:
> >
> >   
> >> Yes, as Dave said, vmap (more specifically: vunmap) is very expensive
> >> because it generally has to invalidate TLBs on all CPUs.
> >>     
> >
> > why is that?  ignoring 32-bit archs we have heaps of address space 
> > available... couldn't the kernel just burn address space and delay global 
> > TLB invalidate by some relatively long time (say 1 second)?
> >   
> 
> Yes, that's precisely the problem.  xfs does delay the unmap, leaving
> stray mappings, which upsets Xen.

sounds like a bug in xen to me :)

-dean

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