Page sharing in Xen?

Page sharing in Xen?

[Jae-Wan Jang]

Hi, folks

I want to know whether Xen shares pages between domains or not.
When I read "Memory Resource Management in VMware ESX server",
they use page sharing between domains with hash value of a page.
So I wonder that Xen uses this technique
or if not, is there anyone who is implementing this to Xen now or
willing to do so.

Thanks in advance.

-- 


Jae-Wan Jang
jwjang@camars.kaist.ac.kr
+82-42-869-3559
http://camars.kaist.ac.kr/~jwjang

Re: Page sharing in Xen?

[Keir Fraser]

On 12 Jul 2006, at 03:38, Jae-Wan Jang wrote:

> I want to know whether Xen shares pages between domains or not.
> When I read "Memory Resource Management in VMware ESX server",
> they use page sharing between domains with hash value of a page.
> So I wonder that Xen uses this technique
> or if not, is there anyone who is implementing this to Xen now or
> willing to do so.

There is explicit page sharing in Xen, but the kind of automatic scheme 
described in that paper. This is largely because it's unclear how great 
the benefit would be in practice.

  -- Keir

Re: Page sharing in Xen?

[Arne Mejlholm]

Hi,

there is actually an implementation, as we spent the last couple of 
semesters doing this for the purpose of evaluation content-based page 
sharing as our master thesis. Our implementation works very similar to 
that of VMware and is built upon the Potemkin framework.

Furthermore we are working on an article to sum up the results.

the code:
http://www.cs.aau.dk/~mejlholm/dat6/cbps/

the thesis:
http://www.cs.aau.dk/library/cgi-bin/detail.cgi?id=1150283144

For information feel free to write us directly :)

Best Regards,
Arne Mejlholm,
Jesper Kristensen and
Jacob Faber Kloster

On Wed, 12 Jul 2006, Keir Fraser wrote:

>
> On 12 Jul 2006, at 03:38, Jae-Wan Jang wrote:
>
>> I want to know whether Xen shares pages between domains or not.
>> When I read "Memory Resource Management in VMware ESX server",
>> they use page sharing between domains with hash value of a page.
>> So I wonder that Xen uses this technique
>> or if not, is there anyone who is implementing this to Xen now or
>> willing to do so.
>
> There is explicit page sharing in Xen, but the kind of automatic scheme 
> described in that paper. This is largely because it's unclear how great the 
> benefit would be in practice.
>
> -- Keir
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
>

Re: Page sharing in Xen?

[Mike D. Day]

Keir Fraser wrote:
> 
> On 12 Jul 2006, at 03:38, Jae-Wan Jang wrote:
> 
>> I want to know whether Xen shares pages between domains or not.
>> When I read "Memory Resource Management in VMware ESX server",
>> they use page sharing between domains with hash value of a page.
>> So I wonder that Xen uses this technique
>> or if not, is there anyone who is implementing this to Xen now or
>> willing to do so.
> 
> There is explicit page sharing in Xen, but the kind of automatic scheme 
> described in that paper. This is largely because it's unclear how great 
> the benefit would be in practice.

Page coalescing is a frequently requested feature, not just for Xen/x86 
but for other platforms/Hypervisors. It would be good if we can 
incorporate it into Xen.

Mike