Re: [Xen-devel] [PATCH 00/11] Alternate p2m: support multiple copies of host p2m

["Jan Beulich" <jbeulich@xxxxxxxx>]

>>> Ed White <edmund.h.white@xxxxxxxxx> 01/13/15 9:03 PM >>>
>On 01/13/2015 11:01 AM, Andrew Cooper wrote:
>> One thing I have noticed while looking at the #VE stuff that EPT also
>> supports A/D tracking, which might be quite a nice optimisation and
>> forgo the need for p2m_ram_logdirty, but I think this should be treated
>> as an orthogonal item.
> 
>This is far from my area of expertise, but I believe there is code in Xen
>to use EPT D bits in migration.

There once was a patch series, but upon asking on the (performance)
benefits, the submitting engineer stated that there was no measurable
improvement, and hence the series never got applied. Right now PML
is being worked on afaik, which from what I can tell will make it a lot
easier (compared to scanning the whole tree for set D bits) to collect
the modified bitmap when the tool stack asks for it.

Jan


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