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

[Juergen Gross <jgross@xxxxxxxx>]

On 11/11/2014 06:47 PM, David Vrabel wrote:
> 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.
I'm not sure I have a machine available with this configuration.

> * 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)
I'll try.


Juergen

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