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Date: Wed, 13 Feb 2013 11:55:38 +0400
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To: Anton Vorontsov <anton@enomsg.org>
CC: <cgroups@vger.kernel.org>, Tejun Heo <tj@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Pekka Enberg <penberg@kernel.org>, Mel Gorman <mgorman@suse.de>,
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Subject: Re: [PATCH] memcg: Add memory.pressure_level events
References: <20130211000220.GA28247@lizard.gateway.2wire.net> <5118C522.3070905@parallels.com> <20130213071922.GB20543@lizard.gateway.2wire.net>
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>>> +void __init enable_pressure_cgroup(void)
>>> +{
>>> +	WARN_ON(cgroup_add_cftypes(&mem_cgroup_subsys,
>>> +				   vmpressure_cgroup_files));
>>> +}
>>
>> There is no functionality discovery going on here, and this is
>> conditional on nothing. Isn't it better then to just add the register +
>> read functions to memcontrol.c and add the files in the memcontrol cftype ?
> 
> I was trying to make the stuff similar to the existing CONFIG_MEMCG_SWAP
> code, which does this kind of adding files to the cgroup. But I can surely
> place files into memcontrol cftype as you suggest.
> 
> Thanks a lot for the comments!
> 
Note that swap can be command line disabled, and in that case we won't
register the files.

Then it makes sense to do it in a separate helper. If I understand your
code correctly, once it is compiled in, it will always be enabled. So I
personally think it is clearer if you register it together with the rest
of the crew.