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Message-ID: <471C1A61.1010001@goop.org>
Date: Sun, 21 Oct 2007 20:34:57 -0700
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: dean gaudet <dean@...tic.org>
CC: Nick Piggin <nickpiggin@...oo.com.au>, David Chinner <dgc@....com>,
xfs@....sgi.com, Xen-devel <xen-devel@...ts.xensource.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Mark Williamson <mark.williamson@...cam.ac.uk>,
Morten Bøgeskov
<xen-users@...ten.bogeskov.dk>, xfs-masters@....sgi.com
Subject: Re: Interaction between Xen and XFS: stray RW mappings
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
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