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Re: [Xen-devel] Re: [Xen-users] Xen 4 - Page Sharing HowTo?

To: Nick Couchman <Nick.Couchman@xxxxxxxxx>, Andrew Lyon <andrew.lyon@xxxxxxxxx>, "pasik@xxxxxx" <pasik@xxxxxx>
Subject: Re: [Xen-devel] Re: [Xen-users] Xen 4 - Page Sharing HowTo?
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Sat, 10 Apr 2010 07:27:28 +0100
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Thread-topic: [Xen-devel] Re: [Xen-users] Xen 4 - Page Sharing HowTo?
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On 09/04/2010 21:45, "Nick Couchman" <Nick.Couchman@xxxxxxxxx> wrote:

>> Sharing opportunities should result in memory being freed back to Xen. So
>> 'xm info', or whatever else you use for monitoring Xen's free memory, should
>> work.
>>  -- Keir
> Hmmm...two XP HVM domUs running, and a total of 7 M freed to Xen.  Kind of
> hard to tell if memory sharing is working, or if this is normal rounding
> behavior...

The two images have to be using a common disc image (or a delta of a common
disc image) exported by a memshr-aware block-device backend: blktap1 or
blktap2. In fact, would have to be the former, since blktap2 has memshr
support disabled as it was crashing. The sharing opportunities aren't
discovered by page scanning, as in some other schemes.

 -- Keir

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