Automatic page sharing/consolidation

Automatic page sharing/consolidation

[Enrico Weigelt]

Hi folks,

I'm using dozens of VE's / jails to separate applications
(even complete webapps w/ their own httpd) for easier maintenance
and better security. But this tends to consume a lot of memory,
since code sharing (.so's) cannot take effect here (each jail/VE
has it's completely own tree). 

Now I wonder if it might be possible to let the kernel automatically
find out equal pages and map them together. 

A little compasion showed up that at least 50% of the code could be
shared (maybe more with some tuning, and maybe even data). So it's
(IMHO) really worth it.

Would this be possible ? What had to be done for this ?


thx
-- 
---------------------------------------------------------------------
 Enrico Weigelt    ==   metux IT service - http://www.metux.de/
---------------------------------------------------------------------
 Please visit the OpenSource QM Taskforce:
 	http://wiki.metux.de/public/OpenSource_QM_Taskforce
 Patches / Fixes for a lot dozens of packages in dozens of versions:
	http://patches.metux.de/
---------------------------------------------------------------------

Re: Automatic page sharing/consolidation

[Avi Kivity]

Enrico Weigelt wrote:
> Hi folks,
>
> I'm using dozens of VE's / jails to separate applications
> (even complete webapps w/ their own httpd) for easier maintenance
> and better security. But this tends to consume a lot of memory,
> since code sharing (.so's) cannot take effect here (each jail/VE
> has it's completely own tree). 
>
> Now I wonder if it might be possible to let the kernel automatically
> find out equal pages and map them together. 
>
> A little compasion showed up that at least 50% of the code could be
> shared (maybe more with some tuning, and maybe even data). So it's
> (IMHO) really worth it.
>
> Would this be possible ? What had to be done for this ?
>   

Izik (copied) is working on this for kvm.  Results so far are very 
encouraging, but currently merged pages are not swappable.

-- 
error compiling committee.c: too many arguments to function

Re: Automatic page sharing/consolidation

[Izik Eidus]

Avi Kivity wrote:
> Enrico Weigelt wrote:
>> Hi folks,
>>
>> I'm using dozens of VE's / jails to separate applications
>> (even complete webapps w/ their own httpd) for easier maintenance
>> and better security. But this tends to consume a lot of memory,
>> since code sharing (.so's) cannot take effect here (each jail/VE
>> has it's completely own tree).
>> Now I wonder if it might be possible to let the kernel automatically
>> find out equal pages and map them together.
>> A little compasion showed up that at least 50% of the code could be
>> shared (maybe more with some tuning, and maybe even data). So it's
>> (IMHO) really worth it.
>>
>> Would this be possible ? What had to be done for this ?
>>   
> 
> Izik (copied) is working on this for kvm.  Results so far are very
> encouraging, but currently merged pages are not swappable.
> 
we have module that posted with kernel patchs in the mm list, you can actualy run it and play with it
there were some bugs that we fixed with it, but i am still not sending it, beacuse i change there quite alot of things
in order to get swapping possible for the pages that are shared.
-- 
woof.