linux-kernel - Re: [PATCH 22/24] HWPOISON: add memory cgroup filter

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Date:	Thu, 3 Dec 2009 10:52:29 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Paul Menage <menage@...gle.com>, Nick Piggin <npiggin@...e.de>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 22/24] HWPOISON: add memory cgroup filter

On Wed, 2 Dec 2009 20:58:42 +0800
Wu Fengguang <fengguang.wu@...el.com> wrote:

> On Wed, Dec 02, 2009 at 08:44:46PM +0800, Andi Kleen wrote:
> > >  
> > > +static int hwpoison_filter_task(struct page *p)
> > > +{
> > 
> > Can we make that ifdef instead of depends on ?
> 
> Sure. Here is the updated patch.
> 
> ---
> HWPOISON: add memory cgroup filter
> 
> The hwpoison test suite need to inject hwpoison to a collection of
> selected task pages, and must not touch pages not owned by them and
> thus kill important system processes such as init. (But it's OK to
> mis-hwpoison free/unowned pages as well as shared clean pages.
> Mis-hwpoison of shared dirty pages will kill all tasks, so the test
> suite will target all or non of such tasks in the first place.)
> 
> The memory cgroup serves this purpose well. We can put the target
> processes under the control of a memory cgroup, and tell the hwpoison
> injection code to only kill pages associated with some active memory
> cgroup.
> 
> The prerequisite for doing hwpoison stress tests with mem_cgroup is,
> the mem_cgroup code tracks task pages _accurately_ (unless page is
> locked).  Which we believe is/should be true.
> 
> The benifits are simplification of hwpoison injector code. Also the
> mem_cgroup code will automatically be tested by hwpoison test cases.
> 
> The alternative interfaces pin-pfn/unpin-pfn can also delegate the
> (process and page flags) filtering functions reliably to user space.
> However prototype implementation shows that this scheme adds more
> complexity than we wanted.
> 
> CC: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> CC: Hugh Dickins <hugh.dickins@...cali.co.uk>
> CC: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
> CC: Balbir Singh <balbir@...ux.vnet.ibm.com>
> CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> CC: Li Zefan <lizf@...fujitsu.com>
> CC: Paul Menage <menage@...gle.com>
> CC: Nick Piggin <npiggin@...e.de> 
> CC: Andi Kleen <andi@...stfloor.org> 
> Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
> ---
>  mm/Kconfig           |    2 +-
>  mm/hwpoison-inject.c |    7 +++++++
>  mm/internal.h        |    1 +
>  mm/memory-failure.c  |   28 ++++++++++++++++++++++++++++
>  4 files changed, 37 insertions(+), 1 deletion(-)
> 
> --- linux-mm.orig/mm/memory-failure.c	2009-12-01 09:56:06.000000000 +0800
> +++ linux-mm/mm/memory-failure.c	2009-12-02 20:56:55.000000000 +0800
> @@ -96,6 +96,31 @@ static int hwpoison_filter_flags(struct 
>  		return -EINVAL;
>  }
>  
> +#ifdef	CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> +u32 hwpoison_filter_memcg;
> +static int hwpoison_filter_task(struct page *p)
> +{
> +	struct mem_cgroup *mem;
> +	struct cgroup_subsys_state *css;
> +
> +	if (!hwpoison_filter_memcg)
> +		return 0;
> +
> +	mem = try_get_mem_cgroup_from_page(p);
> +	if (!mem)
> +		return -EINVAL;
> +
> +	css = mem_cgroup_css(mem);
> +	if (!css)
> +		return -EINVAL;

> +
> +	css_put(css);
> +	return 0;
> +}


Hmm..can you adds comment ? What does this function is for ?

Is this more meaningful than PageLRU(page) etc..?

Thanks,
-Kame

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