[Lxc-users] Resources sharing and limit

[Yanick Emiliano]

Thanks Daniel
It's clear now!! And the test with lxc-execute works perfect!!
I will continue searchs for  memory on demand.
May be someone here is familiar with that!!

On 6 May 2010 11:37, Daniel Lezcano <daniel.lezcano at free.fr> wrote:

> Yanick Emiliano wrote:
>
>> Hi everybody,
>> I have just started playing with lxc and having some difficulties to set
>> cpu
>> and memory on my guests. After my searches, seems that resources
>> controlling
>> is managing in cgroup files and I think that I missed something or I
>> didn't
>> understand how deal with cgroup.
>>
>> After reading cgroup documentation, I understand that:
>> - *cpuset.cpus* indicate to a container the number of cpu available
>>
>
> No exactly, it's a mask of usable cpus for the container. Let's imagine you
> have a 16 cpus machine. The content of cpuset.cpus will be,
> 0-15 which means cpu number 0 to cpu number 15 is used by the cgroup.
>
> If you want to assign the cpu 1 (second cpu) to the container, you have to
> set it by "echo 1 > /cgroup/<name>/cpuset.cpus".
>
> If you want to assign the cpu 1,2,3 to the container, "echo 1,2,3 >
> /cgroup/<name>/cpuset.cpus".
>
> If you want to assign cpu 0 up to 7 to the container, "echo 0-7 >
> /cgroup/<name>/cpuset.cpus".
>
>
> In the context of lxc.
>
> lxc-execute -n foo -s lxc.cgroup.cpuset.cpus="1,2,3" myforks
>
> etc ...
>
>  -*cpuset.cpu_exclusive* limit the number of cpu which the container can
>> use.
>>
>> Am I in good way?
>>
>
> When you assigned the cpus to the container, the processes of the container
> will run on these cpus only but that does not prevent the other tasks of the
> system to run on these cpus. If you want the cpus to be used by the
> container *only*, set them 'exclusive'. This is what I understood.
>
>
>  For example , can I tell to my container that there are 2 cpu available (*
>> cpuset.cpus)*, but use one generally (*puset.cpu_exclusive)*, use the
>> second
>> one only  when it's necessary (when there are a  lot of application to
>> run)?
>>
>
> cpu on demand ? :)
>
> Hey, externally look at the cpu usage of the container, when it reach a
> threshold you define, assign another cpu to the container.
>
>
>  What I want is manage QoS with my containers.
>>
>
> Very likely, you are looking for the cgroup fair scheduler, it would be
> better than dynamically assign cpus to the container, IMHO.
>
> http://lwn.net/Articles/240474/
>
> It's /cgroup/<name>/cpu.shares
>
> Create 2 containers,
>
> lxc-execute -n foo -s lxc.cgroup.cpu.shares=1 /bin/bash
>
> in another shell
>
> lxc-execute -n bar -s /bin/bash
>
>
> in both shell, do "while $(true); do echo -n . ; done"
>
> You will see "foo" displaying the dots veeeery slowly and bar being at the
> normal speed.
>
> As soon as "bar" exits or is frozen (via lxc-freeze), "foo" works at normal
> speed as it is no longer competing the cpu with "bar".
>
> You can dynamically change the priority of the container with "lxc-cgroup
> -n foo cpu.shares=1024" for example.
>
>
>
>  And my last question is, Can I do the same thing with memory sharing?
>>
>
> memory on demand :)
>
> I will let someone else to add comments here, as I am not very familiar
> with memory vs cgroup.
>
> Thanks
>  -- Daniel
>



-- 
Yanick HOUNGBEJI
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