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

From: Avi Kivity
Date: Tue Jun 15 2010 - 03:12:53 EST


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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