RE: [Xen-devel] map memory holes with same page

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> > > But yes, there will be a performance impact because all accesses
to the
> > > missing page will be emulated by sending an ioreq to qemu, so it
will
> > > run _very_ slowly.
> >
> > Isnt that what I just "fixed" for kdump, the new get_mem_type hvmop?
> > Could that be reused for this Windows issue?
> 
> Unfortunately, hibernate tries to compress the pages before handing
them
> over to the driver, so there isn't a point where the driver can avoid
> the access.  If there were such a point, the balloon driver could work
> around it from its own records, without even needing the hypercall.
> 

I hypercall might be faster than wading through a list of pfn's.
Especially in the dump driver where you are supposed to trust as little
of the system as possible.

James

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