Re: Interaction between Xen and XFS: stray RW mappings

Jeremy Fitzhardinge
2007-10-22T03:35:09Z

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.

J