Re: [RFD] Merge task counter into memcg

From: Frederic Weisbecker
Date: Wed Apr 18 2012 - 03:53:01 EST

2012/4/18 KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>:
> (2012/04/18 1:52), Glauber Costa wrote:
>>>> 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.
>>> So, you think that while kmem would be enough to prevent fork-bombs,
>>> it would still make sense to limit in more traditional ways
>>> (ie. ulimit style object limits).  Hmmm....
>> I personally think this is namespaces business, not cgroups.
>> If you have a process namespace, an interface that works to limit the
>> number of processes should keep working given the constraints you are
>> given.
>> What doesn't make sense, is to create a *new* interface to limit
>> something that doesn't really need to be limited, just because you
>> limited a similar resource before.
> Ok, limitiing forkbomb is unnecessary. ulimit+namespace should work.
> What we need is user-id namespace, isn't it ? If we have that, ulimit
> works enough fine, no overheads.

I have considered using NR_PROC rlimit on top of user namespaces to
fight forkbombs inside a container.
ie: one user namespace per container with its own rlimit.

But it doesn't work because we can have multiuser apps running in a
single container.
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