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Date: Thu, 20 Sep 2012 15:33:23 -0700 (PDT)
From: David Rientjes <rientjes@google.com>
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To: Michal Hocko <mhocko@suse.cz>
cc: Tejun Heo <tj@kernel.org>, containers@lists.linux-foundation.org,
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        "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
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Subject: Re: [PATCH 2.6.32] memcg: warn on deeper hierarchies with
 use_hierarchy==0
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On Thu, 20 Sep 2012, Michal Hocko wrote:

> Yes printk_once is an alternative but I really wanted to have this as
> much visible as possible. People tend to react to stack traceces more
> and this one will trigger only if somebody is either doing something
> wrong or the configuration is the one we are looking for.
> 

That's the complete opposite of what Linus has said he wants, he said very 
specifically that he doesn't want WARN_ONCE() or WARN_ON_ONCE() for 
deprecation of tunables.  If you want to have this merged, then please get 
him to ack it.

> Comparing to oom_adj, that one was used much more often so the WARN_ONCE
> was too verbose especially when you usually had to wait for an userspace
> update which is not the case here.

How is WARN_ONCE() too verbose for oom_adj?  It's printed once!  And how 
can you claim that userspace doesn't need to change if it's creating a 
hierarchy while use_hierarchy == 0?