linux-kernel - Re: [PATCH v3 0/3] cgroup: add xattr support

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Message-ID: <20120807152230.GE20962@cathedrallabs.org>
Date:	Tue, 7 Aug 2012 11:22:30 -0400
From:	Aristeu Rozanski <aris@...vo.org>
To:	Tejun Heo <tj@...nel.org>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Aristeu Rozanski <aris@...hat.com>,
	linux-kernel@...r.kernel.org, Li Zefan <lizefan@...wei.com>,
	Hillf Danton <dhillf@...il.com>, lennart@...ttering.net
Subject: Re: [PATCH v3 0/3] cgroup: add xattr support

(Added Lennart to the discussion so he can help explaining how systemd will
use the xattrs)

On Fri, Jul 20, 2012 at 11:04:59AM -0700, Tejun Heo wrote:
> Hello, Hugh, Aristeu.
> 
> On Fri, Jul 20, 2012 at 01:59:59PM -0400, Aristeu Rozanski wrote:
> > hm, not sure that's what Tejun meant. tmpfs uses anonymous memory for the file
> > contents, so reuse that infrastructure to allocate space for the extended
> > attributes the same way, instead of using kmem.
> > 
> > First thing I can think of is to use whole pages for it to prevent further
> > complexity. Shouldn't make much difference considering the usecases we have
> > now (systemd and containers), right?
> 
> Yeah, that's what I meant.  The internal fragmentation is ugly but I
> think that should do for now at least.

while talking to Lennart, it seems there're a lot of ways the xattrs can be
used in systemd. If we're concerned with the amount of memory used, why not
create a new namespace just for this, limiting by definition the maximum value
size?

-- 
Aristeu

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