[libvirt] [PATCH] get memory in openvz driver

[Evgeniy Sokolov]

> On Thu, Aug 14, 2008 at 06:08:31PM +0400, Evgeniy Sokolov wrote:
>>> On Wed, Aug 13, 2008 at 12:50:33PM +0400, Evgeniy Sokolov wrote:
>>>> OpenVZ has several parameters for memory management. All of them can be 
>>>> configured independetly.
>>> Summing all the different memory limits together is wrong - this will
>>> make it impossible to implement a 'setMemory' operation because you've
>>> now no way of deciding which parameter to set.
>> It is correct calcuation of total memory.
>> Because of non-obvious implenetation of 'setMemory', I have asked 'how 
>> to manage memory' in begining.
>> I propouse to set some portion of 'memory' to each limit.
> 
> I don't think that will be lead to good behaviour - ultimtely I think
> we'll need to expose more (all?) of these memory settings directly as
> tunable resources.
Good idea! 5 setting for low memory + application
  THus for the 'memory' setting we which pick the
> value which provides the primary memory size as available to apps
> within the container.
> 
>>> In my testing the total memory inside a OpenVZ container seems to 
>>> correspond to the 'lockedpages' parameter, so we should just return
>>> that value.
>> How did you get total memory?
>> Most big part of memory is oomguarpages (by default). Lockedpages is 
>> about %1.
> 
> I've just found & read these descriptions...
> 
>   http://wiki.openvz.org/Oomguarpages#oomguarpages 
>   http://wiki.openvz.org/Oomguarpages#privvmpages
>   http://wiki.openvz.org/Vmguarpages#vmguarpages
> 
> To summarize 
> 
>     "Oomguarpages parameter accounts the total amount of memory and
>      swap space used by the processes of a particular container.
> 
>     "Privvmpages parameter accounts allocated (but, possibly, not 
>      used yet) memory. The accounted value is an estimation how 
>      much memory will be really consumed when the container's 
>      applications start to use the allocated memory. Consumed 
>      memory is accounted into oomguarpages parameter
> 
>     "vmguarpages parameter controls how much memory is available to
>      the Virtual Environment (i.e. how much memory its applications
>      can allocate by malloc(3) or other standard Linux memory 
>      allocation mechanisms"
> 
>     "The memory allocation guarantee (vmguarpages) is a primary tool
>      for controlling the memory available to containers, because it
>      allows administrators to provide Service Level Agreements"
> 
> So from those I'd think that 'vmguarpages'  maps best into libvirt's 
> concept of 'memory'. Though perhaps 'oomguardpages' could be set for
> 'memory' and 'vmguarpages' used for 'max memory'
Oomguarpages & Privvmpages & vmguarpages are settings for apps memory.

We may
1 set 'memory' to 'privvmpages' - then free will show correct value.
2 set 'memory' to 'vmguarpages' or 'oomguardpages' and
'maxmemory' to 'privvmpages'.

What do 'MaxMemory' mean for other libvirt drivers?

Bad point of it, for example:
We can set many of Oomguarpages & Privvmpages & vmguarpages but 
application can not start because of 'kmemsize' is over.

> 
> Daniel