Date: Thu, 10 Dec 2009 07:51:13 +0530
From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Paul Menage <menage@google.com>, kosaki.motohiro@jp.fujitsu.com,
       hugh.dickins@tiscali.co.uk, nishimura@mxp.nes.nec.co.jp,
       kamezawa.hiroyu@jp.fujitsu.com, lizf@cn.fujitsu.com, npiggin@suse.de,
       fengguang.wu@intel.com, linux-kernel@vger.kernel.org,
       linux-mm@kvack.org
Subject: Re: [PATCH] [23/31] HWPOISON: add memory cgroup filter
Message-ID: <20091210022113.GJ3722@balbir.in.ibm.com>
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* Andi Kleen <andi@firstfloor.org> [2009-12-10 02:42:12]:

> > While the functionality sounds useful, the interface (passing an inode
> > number) feels a bit ugly to me. Also, if that group is deleted and a
> > new cgroup created, you could end up reusing the inode number.
> 
> Please note this is just a testing interface, doesn't need to be
> 100% fool-proof. It'll never be used in production.
> 
> > 
> > How about an approach where you write either the cgroup path (relative
> > to the memcg mount) or an fd open on the desired cgroup? Then you
> > could store a (counted) css reference rather than an inode number,
> > which would make the filter function cleaner too, since it would just
> > need to compare css objects.
> 
> Sounds complicated, I assume it would be much more code?
> I would prefer to keep the testing interfaces as simple as possible.
>

We do this for cgroupstats and the code is not very complicated. In
case you want to look, the user space code is at
Documentation/accounting/getdelays.c and the kernel code is in
kernel/taskstats.c 

-- 
	Balbir
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