Messages in this thread | | | Date | Mon, 28 Jul 2014 14:18:17 +0100 | From | David Vrabel <> | Subject | Re: [PATCH v2 2/2] xen/setup: Remap Xen Identity Mapped RAM |
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On 20/07/14 01:01, 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
This looks like a worthwhile improvement but...
> arch/x86/xen/setup.c | 370 +++++++++++++++++++++++++++++++++++++++-----------
... Ew :(
It will take me a bit longer before I can give this a proper review.
David
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