| To: | dean gaudet <dean@xxxxxxxxxx> |
|---|---|
| Subject: | [xfs-masters] Re: Interaction between Xen and XFS: stray RW mappings |
| From: | Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
| Date: | Sun, 21 Oct 2007 20:34:57 -0700 |
| Cc: | Nick Piggin <nickpiggin@xxxxxxxxxxxx>, David Chinner <dgc@xxxxxxx>, xfs@xxxxxxxxxxx, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Mark Williamson <mark.williamson@xxxxxxxxxxxx>, Morten Bøgeskov <xen-users@xxxxxxxxxxxxxxxxxx>, xfs-masters@xxxxxxxxxxx |
| In-reply-to: | <alpine.DEB.0.9999.0710212015430.2320@xxxxxxxxxxxxxxxxxxx> |
| References: | <470FA7C3.90404@xxxxxxxx> <20071014225618.GN23367404@xxxxxxx> <4712A254.4090604@xxxxxxxx> <200710151415.07248.nickpiggin@xxxxxxxxxxxx> <alpine.DEB.0.9999.0710212015430.2320@xxxxxxxxxxxxxxxxxxx> |
| Reply-to: | xfs-masters@xxxxxxxxxxx |
| Sender: | xfs-masters-bounce@xxxxxxxxxxx |
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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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