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xen-devel
[Xen-devel] Re: [PATCH RFC] vmalloc: eagerly clear ptes on vunmap
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To: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Subject: |
[Xen-devel] Re: [PATCH RFC] vmalloc: eagerly clear ptes on vunmap |
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From: |
Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> |
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Date: |
Tue, 30 Nov 2010 16:29:38 -0800 |
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Cc: |
Bryan, "Xen-devel@xxxxxxxxxxxxxxxxxxx" <Xen-devel@xxxxxxxxxxxxxxxxxxx>, Nick Piggin <npiggin@xxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Schumaker <bjschuma@xxxxxxxxxx>, Linux Memory Management List <linux-mm@xxxxxxxxx> |
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Tue, 30 Nov 2010 16:31:04 -0800 |
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On Mon, 29 Nov 2010 12:32:11 -0800
Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
> When unmapping a region in the vmalloc space, clear the ptes immediately.
> There's no point in deferring this because there's no amortization
> benefit.
>
> The TLBs are left dirty, and they are flushed lazily to amortize the
> cost of the IPIs.
>
> This specific motivation for this patch is a regression since 2.6.36 when
> using NFS under Xen, triggered by the NFS client's use of vm_map_ram()
> introduced in 56e4ebf877b6043c289bda32a5a7385b80c17dee. XFS also uses
> vm_map_ram() and could cause similar problems.
>
Do we have any quantitative info on that regression? The patch fixed
it, I assume?
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