Re: [RFC/T/D][PATCH 2/2] Linux/Guest cooperative unmapped page cachecontrol

[Avi Kivity]

On 06/14/2010 08:16 PM, Balbir Singh wrote:
> * Dave Hansen<dave@xxxxxxxxxxxxxxxxxx>  [2010-06-14 10:09:31]:
>
>    
> > On Mon, 2010-06-14 at 22:28 +0530, Balbir Singh wrote:
> >      
> > > If you've got duplicate pages and you know
> > > that they are duplicated and can be retrieved at a lower cost, why
> > > wouldn't we go after them first?
> > >        
> > I agree with this in theory.  But, the guest lacks the information about
> > what is truly duplicated and what the costs are for itself and/or the
> > host to recreate it.  "Unmapped page cache" may be the best proxy that
> > we have at the moment for "easy to recreate", but I think it's still too
> > poor a match to make these patches useful.
> >
> >      
> That is why the policy (in the next set) will come from the host. As
> to whether the data is truly duplicated, my experiments show up to 60%
> of the page cache is duplicated.

Isn't that incredibly workload dependent?

We can't expect the host admin to know whether duplication will occur or 
not.

--
error compiling committee.c: too many arguments to function

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