Re: [RFD] Merge task counter into memcg

[Glauber Costa]

On 04/12/2012 10:42 PM, KAMEZAWA Hiroyuki wrote:
> To be honest, I doubt that task counter is unnecessary...memcg can catch
> oom situation well. I often test 'make -j' under memcg.
>
> To the questions
> *   It sounds like a 'ulimit' cgroup. How about overwriting
>      ulimit values via cgroup ? (sounds joke?) Then, overhead will be small but
>      I'm not sure it can be hierarchical and doesn't break userland.
>
>      If people wants to limit the number of tasks, I think interface should provide it
>      in the unit of objects. Then, I'm ok to have other subsystem for counting something.
>      fork-bomb's memory overhead can be prevent by memcg. What memcg cannot handle
>      is ulimit. If forkbomb exhausts all ulimit/tasks, the user cannot login.
>      So, having task-limit cgroup subsys for a sandbox will make sense in some situation.
>
> In short, I don't think it's better to have task-counting and fd-counting in memcg.
> It's kmem, but it's more than that, I think.
> Please provide subsys like ulimit.
Kame,

You're talking about the memcg that is in the kernel today.
I think the discussion is orbiting around how it is going to be once we
start tracking kernel memory like the slab (for task_struct), or kernel 
stack pages.

In those scenarios, a fork bomb will be stopped anyway, because it will 
need kernel memory it can't grab.

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