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Query on host swapping of guest pages. [message #31668] Sat, 05 July 2008 05:42 Go to next message
Arn is currently offline  Arn
Messages: 2
Registered: July 2008
Junior Member
From: openvz.org
Hi,

I need to know the following for some experiments I'm doing as part of
a school project:

Does OpenVZ support host swapping of guest pages ? That is : if a host
experiences memory pressure, can it swap out some of a guest's (guest
vm) pages and use them ? I assume that if this is possible then when
the guest needs to use the memory again it will be swapped back in ?
Can someone confirm if OpenVz does this ?

Also, can the host change the memory allocation for a guest at runtime
(while the guest is running) ?

Thanks
Arn
Re: Query on host swapping of guest pages. [message #31684 is a reply to message #31668] Sun, 06 July 2008 18:19 Go to previous messageGo to next message
Kirill Korotaev is currently offline  Kirill Korotaev
Messages: 137
Registered: January 2006
Senior Member
From: openvz.org
Arn wrote:
> Hi,
> 
> I need to know the following for some experiments I'm doing as part of
> a school project:
> 
> Does OpenVZ support host swapping of guest pages ? That is : if a host
> experiences memory pressure, can it swap out some of a guest's (guest
> vm) pages and use them ? I assume that if this is possible then when
> the guest needs to use the memory again it will be swapped back in ?
> Can someone confirm if OpenVz does this ?

yes, it does.

> Also, can the host change the memory allocation for a guest at runtime
> (while the guest is running) ?

not sure what you mean...


> 
> Thanks
> Arn
>
Re: Query on host swapping of guest pages. [message #31688 is a reply to message #31684] Mon, 07 July 2008 02:47 Go to previous messageGo to next message
Arn is currently offline  Arn
Messages: 2
Registered: July 2008
Junior Member
From: openvz.org
On Sun, Jul 6, 2008 at 2:19 PM, Kirill Korotaev <dev@parallels.com> wrote:
>
>> Does OpenVZ support host swapping of guest pages ? That is : if a host
>> experiences memory pressure, can it swap out some of a guest's (guest
>> vm) pages and use them ? I assume that if this is possible then when
>> the guest needs to use the memory again it will be swapped back in ?
>> Can someone confirm if OpenVz does this ?
>
> yes, it does.
>
>> Also, can the host change the memory allocation for a guest at runtime
>> (while the guest is running) ?
>
> not sure what you mean...

Kirill, thanks for the response.

What I mean is that if we specify that a guest VM has say 512 MB of
physical RAM when we are initalizing/starting the VM then can we
change it later while the guest is still running. That is, can I later
reduce or increase the amount of physical RAM the guest VM has without
restarting it ?

Thanks
Arn
Re: Query on host swapping of guest pages. [message #31691 is a reply to message #31688] Mon, 07 July 2008 05:15 Go to previous message
Kirill Korotaev is currently offline  Kirill Korotaev
Messages: 137
Registered: January 2006
Senior Member
From: openvz.org
Arn wrote:
> On Sun, Jul 6, 2008 at 2:19 PM, Kirill Korotaev <dev@parallels.com> wrote:
>>> Does OpenVZ support host swapping of guest pages ? That is : if a host
>>> experiences memory pressure, can it swap out some of a guest's (guest
>>> vm) pages and use them ? I assume that if this is possible then when
>>> the guest needs to use the memory again it will be swapped back in ?
>>> Can someone confirm if OpenVz does this ?
>> yes, it does.
>>
>>> Also, can the host change the memory allocation for a guest at runtime
>>> (while the guest is running) ?
>> not sure what you mean...
> 
> Kirill, thanks for the response.
> 
> What I mean is that if we specify that a guest VM has say 512 MB of
> physical RAM when we are initalizing/starting the VM then can we
> change it later while the guest is still running. That is, can I later
> reduce or increase the amount of physical RAM the guest VM has without
> restarting it ?

yes.

Kirill
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