[Devel] [PATCH] cgroups: fix set command with beancounters upstream

[Kir Kolyshkin]

On 04/30/2013 03:17 AM, Glauber Costa wrote:
> On 04/30/2013 01:48 PM, Kir Kolyshkin wrote:
>> On 04/29/2013 10:12 PM, Glauber Costa wrote:
>>> The kernel memory controller cannot flip states from unlimited to
>>> limited if
>>> there are already tasks in it.  Therefore, we always have to run with
>>> *some*
>>> value of kmem enabled. If we don't do it, we can't start unlimited and
>>> then use
>>> the set command to set any beancounters. We write the maximum amount
>>> minus two
>>> pages, which should effectively mean "accounting turned on, but
>>> unlimited"
>> Alternatively, we can require CT restart for the change to take effect.
>> We do that for a few options, see check_set_mode().
>>
>> But this is probably OK too.
> Being all the same to you, I prefer this way. This is not really about
> "container running", but rather "cgroups have tasks". Doing it on
> restart would still mandate us to always be careful about when to set up
> cgroup limits and always do that before we put any tasks into it. Of
> course we can do that, but not having that limitation makes us more
> robust IMHO. We also already have a lot of non-limit related stuff that
> we have to do during creation anyway (like setting up cpusets and memory
> hierarchy), so it just fits together nicely
>
applied