[Xen-devel] Re: [PATCH RFC] vmalloc: eagerly clear ptes on vunmap

[Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>]

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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