Re: [Xen-devel] [PATCH v3 2/2] xen/setup: Remap Xen Identity Mapped RAM

[Matthew Rushton <mvrushton@xxxxxxxxx>]

On 08/11/14 10:41, Matt Wilson wrote:
> On Mon, Aug 11, 2014 at 10:34:01AM -0700, Matt Rushton wrote:
> > Instead of ballooning up and down dom0 memory this remaps the existing mfns
> > that were replaced by the identity map. The reason for this is that the
> > existing implementation ballooned memory up and and down which caused dom0
> > to have discontiguous pages. In some cases this resulted in the use of bounce
> > buffers which reduced network I/O performance significantly. This change will
> > honor the existing order of the pages with the exception of some boundary
> > conditions.
> >
> > To do this we need to update both the Linux p2m table and the Xen m2p table.
> > Particular care must be taken when updating the p2m table since it's important
> > to limit table memory consumption and reuse the existing leaf pages which get
> > freed when an entire leaf page is set to the identity map. To implement this,
> > mapping updates are grouped into blocks with table entries getting cached
> > temporarily and then released.
> >
> > On my test system before:
> > Total pages: 2105014
> > Total contiguous: 1640635
> >
> > After:
> > Total pages: 2105014
> > Total contiguous: 2098904
> >
> > Signed-off-by: Matthew Rushton <mrushton@xxxxxxxxxx>
> > ---
> Matt,
>
> Could you provide a summary of v2->v3 changes here?
>
> --msw
>
> >   arch/x86/xen/p2m.c   |   23 +---
> >   arch/x86/xen/p2m.h   |   15 ++
> >   arch/x86/xen/setup.c |  370 +++++++++++++++++++++++++++++++++++++++-----------
> >   3 files changed, 314 insertions(+), 94 deletions(-)
> >   create mode 100644 arch/x86/xen/p2m.h
Resent patch set with:

v3: One line change to fix 32-bit mfn casting issue with MMU_MACHPHYS_UPDATE


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