[Devel] Re: [lxc-devel] Memory Resources

[Daniel Lezcano]

Serge E. Hallyn wrote:
> Quoting Daniel Lezcano (daniel.lezcano at free.fr):
>   
>> Krzysztof Taraszka wrote:
>>     
>>> Okey.
>>> I made few tests and this two ways work:
>>>
>>> First way:
>>> =======
>>> lxc. smack enabled, policy loaded. cgroup not labeled.
>>>
>>> a) start container
>>> b) mount cgroup inside container
>>> c) mount --bind /cgroup/foo/memory.meminfo /proc/meminfo
>>> d) secure the /cgroup on the host (ie: attr -S -s SMACK64 -V host /cgroup).
>>>
>>> this step can be done inside lxc tools ;)
>>>
>>> Second way:
>>> ==========
>>> lxc. smack enabled, policy loaded. cgroup not labeled.
>>>
>>> a) do not label whole /cgrop directory (DO NOT DO: attr -S -s SMACK64 -V
>>> host /cgroup). Label dedicate files only (for example: /cgroup/cpuset.cpus,
>>> /cgroup/vs1/cpuset.cpus, etc). Do not label the /cgrop/vs1 directory. Label
>>> with vs1 label only /cgroup/vs1/memory.meminfo. All other files label with
>>> host label to do not allow read them.
>>> b) start container
>>> c) mount cgroup inside container
>>> d) mount --bind /cgroup/foo/memory.meminfo /proc/meminfo
>>>
>>> steps: b, c, d can be done inside lxc tools. step a can't and it is base on
>>> the admin policy.
>>>
>>> I think that the first solution is more automatic and can be done by lxc
>>> tools (maybe command line switch? I can prepare a patch for that.
>>>   
>>>       
>> I do not know smack, what does smack here ? Will this solution avoid the 
>> container to overwrite /proc/meminfo by remounting /proc ?
>>     
>
> Right, in the first way he is labeling the whole cgroupfs with a label
> which prevents the container from mounting it.  In the second way,
> the specific files are labeled.
>   

Ah, got it ! :)

The idea of Kamezawa-san to use a fuse proc is maybe a good idea in this 
case. So we can address the entire /proc specific informations. For 
example, like the /proc/meminfo, there is the /proc/cpuinfo. If you 
restrict the usage to a subset of your cpus with cpuset and you look at 
/proc/cpuinfo, you see all the cpus; it is not a big problem until a 
computation application looks at this file and choose to fork(n cpus) 
and set the affinity of each process to each cpu ... AFAIR, this is the 
case for HPC applications.

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