linux-kernel - Re: memcg: cat: memory.memsw.* : Operation not supported

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Message-ID: <20120627200926.GR15811@google.com>
Date:	Wed, 27 Jun 2012 13:09:26 -0700
From:	Tejun Heo <tj@...nel.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Michal Hocko <mhocko@...e.cz>, Zhouping Liu <zliu@...hat.com>,
	linux-mm@...ck.org, Li Zefan <lizefan@...wei.com>,
	CAI Qian <caiqian@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: memcg: cat: memory.memsw.* : Operation not supported

Hello, Michal, David.

On Wed, Jun 27, 2012 at 01:04:51PM -0700, David Rientjes wrote:
> I think it's a crappy solution and one that is undocumented in 
> Documentation/cgroups/memory.txt.  If you can only enable swap accounting 
> at boot either via .config or the command line then these files should 
> never be added for CONFIG_CGROUP_MEM_RES_CTLR_SWAP=n or when 
> do_swap_account is 0.  It's much easier to test if the feature is enabled 
> by checking for the presence of these files at the memcg mount point 
> rather than doing an open(2) and checking for -EOPNOTSUPP, which isn't 
> even a listed error code.  I don't care how much cleaner it makes the 
> internal memcg code.

Yeah, it's kinda ugly.  Taking a step back, do we really need be able
to configure out memsw?  How much vmlinux bloat or runtime overhead
are we talking about?  I don't think config options need to be this
granular.

Thanks.

-- 
tejun
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