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Date: Fri, 11 Dec 2009 10:14:05 +0800 From: Wu Fengguang <fengguang.wu@...el.com> To: Balbir Singh <balbir@...ux.vnet.ibm.com> Cc: Andi Kleen <andi@...stfloor.org>, Paul Menage <menage@...gle.com>, "kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>, "hugh.dickins@...cali.co.uk" <hugh.dickins@...cali.co.uk>, "nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>, "kamezawa.hiroyu@...fujitsu.com" <kamezawa.hiroyu@...fujitsu.com>, "lizf@...fujitsu.com" <lizf@...fujitsu.com>, "npiggin@...e.de" <npiggin@...e.de>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, "Li, Haicheng" <haicheng.li@...el.com> Subject: Re: [PATCH] [23/31] HWPOISON: add memory cgroup filter On Thu, Dec 10, 2009 at 10:21:13AM +0800, Balbir Singh wrote: > * Andi Kleen <andi@...stfloor.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, thanks for the tip. We could keep an fd open on the desired cgroup, in user space: #!/bin/bash mkdir /cgroup/hwpoison && \ exec 9<>/cgroup/hwpoison/tasks || exit 1 A bit simpler than an in-kernel fget_light() or CSS refcount :) Thanks, Fengguang -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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