Re: [Xen-devel] [PATCH V3 7/8] xen: switch to linear virtual mapped sparse p2m list

[David Vrabel]

On 11/11/14 05:43, Juergen Gross wrote:
> At start of the day the Xen hypervisor presents a contiguous mfn list
> to a pv-domain. In order to support sparse memory this mfn list is
> accessed via a three level p2m tree built early in the boot process.
> Whenever the system needs the mfn associated with a pfn this tree is
> used to find the mfn.
> 
> Instead of using a software walked tree for accessing a specific mfn
> list entry this patch is creating a virtual address area for the
> entire possible mfn list including memory holes. The holes are
> covered by mapping a pre-defined  page consisting only of "invalid
> mfn" entries. Access to a mfn entry is possible by just using the
> virtual base address of the mfn list and the pfn as index into that
> list. This speeds up the (hot) path of determining the mfn of a
> pfn.
> 
> Kernel build on a Dell Latitude E6440 (2 cores, HT) in 64 bit Dom0
> showed following improvements:
> 
> Elapsed time: 32:50 ->  32:35
> System:       18:07 ->  17:47
> User:        104:00 -> 103:30
> 
> Tested on 64 bit dom0 and 32 bit domU.

Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>

Can you please test this with the following guests/scenarios.

* 64 bit dom0 with PCI devices with high MMIO BARs.
* 32 bit domU with PCI devices assigned.
* 32 bit domU with 64 GiB of memory.
* domU that starts pre-ballooned and is subsequently ballooned up.
* 64 bit domU that is saved and restored (or local host migration)
* 32 bit domU that is saved and restored (or local host migration)

Thanks.

David
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