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Re: [Xen-users] Re: Xen 4.0 memory overcommitment

To: Miguel <miguelrvs@xxxxxxxxx>
Subject: Re: [Xen-users] Re: Xen 4.0 memory overcommitment
From: Antoine Benkemoun <antoine.benkemoun@xxxxxxxxx>
Date: Wed, 28 Apr 2010 11:46:44 +0200
Cc: Xen List <xen-users@xxxxxxxxxxxxxxxxxxx>
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Hello,

Thank you for your help. I have seen the mentionned information.

I am understanding that the initial memory allocation given to a domain is the absolute minimum it can use. After that, you can increase it on overcommitment pools. Is this even right ?

I am surprised to find so little information about such a great and useful feature. This usually means I am missing something big...

Antoine

2010/4/27 Miguel <miguelrvs@xxxxxxxxx>
2010/4/27 Martinx - ジェームズ <thiagocmartinsc@xxxxxxxxx>:
> I guess you should learn the Transcendent Memory
> (http://oss.oracle.com/projects/tmem/) from Oracle...
> Am I right?
> Cheers!
> Thiago
>
> On 26 April 2010 05:54, Antoine Benkemoun <antoine.benkemoun@xxxxxxxxx>
> wrote:
>>
>> Does anyone have any pointers concerning memory overcommitment ?
>>
>> Thank you in advance for your help,
>>
>> Antoine
>>
>> On Wed, Apr 21, 2010 at 10:23 PM, Antoine Benkemoun
>> <antoine.benkemoun@xxxxxxxxx> wrote:
>>>
>>> Hello,
>>>
>>> I am running a functional Xen 4.0 platform. The objective is the project
>>> I am currently running is to replace 4 VMWare ESX by 4 Xen 4.0 hypervisors.
>>> I have been able to reproduce all the core VMWare features in Xen (but
>>> better of course =D) except memory overcommitment.
>>>
>>> I know this feature has been included since Xen 3.3 but I have found
>>> almost no information about it.
>>>
>>> When I try to start a domain with more RAM then is available on the
>>> server I get the following message :
>>>
>>> VmError: I need 1433600 KiB, but dom0_min_mem is 200704 and shrinking to
>>> 200704 KiB would leave only 1348320 KiB free.
>>>
>>> Well I know it doesn't have enough RAM, that's the whole point. Do I need
>>> to enable something specific somewhere ? I am using the Jeremy's 2.6.31
>>> kernel (thank you whoever you may be !).
>>>
>>> Thank you in advance for your help,
>>>
>>> Antoine

You may want to read about the balloon driver in xen.
http://wiki.xensource.com/xenwiki/XenFaq#head-ff507535c38a3191053dad83d8d68d19c5482e70

Miguel

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