linux-kernel - Re: [PATCH 0/2] resource control file system

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Message-ID: <20070305174750.GA14507@in.ibm.com>
Date:	Mon, 5 Mar 2007 23:17:50 +0530
From:	Srivatsa Vaddagiri <vatsa@...ibm.com>
To:	Paul Jackson <pj@....com>
Cc:	Herbert Poetzl <herbert@...hfloor.at>, dev@...nvz.org,
	ebiederm@...ssion.com, winget@...gle.com,
	containers@...ts.osdl.org, menage@...gle.com,
	ckrm-tech@...ts.sourceforge.net, xemul@...ru,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] resource control file system - aka containers on top of nsproxy!

On Sat, Mar 03, 2007 at 01:22:44PM -0800, Paul Jackson wrote:
> I still can't claim to have my head around this, but what you write
> here, Herbert, writes here touches on what I suspect is a key
> difference between namespaces and resources that would make it
> impractical to accomplish both with a shared mechanism for aggregating
> tasks.

The way nsproxy is structured, its all pointers to actual namespace (or
in case of rcfs patch) resource objects.  This lets namespaces objects be in a 
flat hierarchy while resource objects are in tree-like hierarchy.
nsproxy itself doesnt decide any hierarchy. Its those objects pointed to
by nsproxy which can form different hierarchies. In fact the rcfs
patches allows such a combination afaics.

> > on every limit accounting or check? I think that
> > is quite a lot of overhead ...
> 
> Do either of these dereferences require locks?

A rcu_read_lock() should be required, which is not that expensive.

-- 
Regards,
vatsa
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