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

From: Balbir Singh
Date: Mon Jun 14 2010 - 13:16:56 EST

* 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. The first patch today is again
enabled by the host. Both of them are expected to be useful in the
cache != none case.

The data I have shows more details including the performance and

Three Cheers,
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