linux-kernel - Re: [RFC][PATCH 0/4] memcg: add support for hwpoison testing

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Date:	Tue, 1 Sep 2009 08:46:26 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
	lizf@...fujitsu.com, nishimura@....nes.nec.co.jp,
	menage@...gle.com, linux-mm <linux-mm@...ck.org>
Subject: Re: [RFC][PATCH 0/4] memcg: add support for hwpoison testing

On Mon, 31 Aug 2009 18:26:40 +0800
Wu Fengguang <fengguang.wu@...el.com> wrote:

> Hi all,
> 
> In hardware poison testing, we want to inject hwpoison errors to pages
> of a collection of selected tasks, so that random tasks (eg. init) won't
> be killed in stress tests and lead to test failure.
> 
> Memory cgroup provides an ideal tool for tracking and testing these target
> process pages. All we have to do is to
> - export the memory cgroup id via cgroupfs
> - export two functions/structs for hwpoison_inject.c
> 
> This might be an unexpected usage of memory cgroup. The last patch and this
> script demonstrates how the exported interfaces are to be used to limit the
> scope of hwpoison injection.
> 
> 	test -d /cgroup/hwpoison && rmdir /cgroup/hwpoison
> 	mkdir /cgroup/hwpoison
> 
> 	usemem -m 100 -s 100 &   # eat 100MB and sleep 100s
> 	echo `pidof usemem` > /cgroup/hwpoison/tasks
> 
> ==>     memcg_id=$(</cgroup/hwpoison/memory.id)
> ==>     echo $memcg_id > /debug/hwpoison/corrupt-filter-memcg
> 
> 	# hwpoison all pfn
> 	pfn=0
> 	while true
> 	do      
> 		let pfn=pfn+1
> 		echo $pfn > /debug/hwpoison/corrupt-pfn
> 		if [ $? -ne 0 ]; then
> 			break
> 		fi
> 	done
> 

I don't like this.

1. plz put all under CONFIG_DEBUG_HWPOISON or some
2. plz don't export memcg's id. you can do it without it.
3. If I was you, just adds following file

	memory.hwpoison_test
   Then, if you allow test
	#echo 1 >	memory.hwpoison_test

4. I can't understand why you need this. I wonder you can get pfn via
   /proc/<pid>/????. And this may insert HWPOISON to page-cache of shared
   library and "unexpected" process will be poisoned.

Thanks,
-Kame

> Comments are welcome, thanks!
> 
> Cheers,
> Fengguang
> -- 
> 
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