[Xen-devel] Re: [PATCH] xen: core dom0 support

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Anthony Liguori wrote:
> Jeremy Fitzhardinge wrote:
> > Nick Piggin wrote:
> > It really depends on the workload.  There's three cases to consider: 
> > software shadow pagetables, hardware nested pagetables, and Xen 
> > direct pagetables.  Even now, Xen's (highly optimised) shadow 
> > pagetable code generally out-performs modern nested pagetables, at 
> > least when running Windows (for which that code was most heavily tuned).
> Can you point to benchmarks?  I have a hard time believing this.
Erm, not that I know of off-hand.  I don't really have any interest in 
Windows performance, so I'm reduced to repeating (highly reliable) Xen 
Summit corridor chat.
> How can shadow paging beat nested paging assuming the presence of 
> large pages? 
I think large pages do turn the tables, and its close to parity with 
shadow with 4k pages on recent cpus.  But see above for reliability on 
that info.
   J


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