linux-kernel - [PATCH 0/2] memcg: fix oom handling

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Date:	Fri, 21 Nov 2008 18:58:29 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	pbadari@...ibm.com, jblunck@...e.de, taka@...inux.co.jp,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	npiggin@...e.de
Subject: [PATCH 0/2] memcg: fix oom handling


Li Zefan reported

(a) This goes dead lock:
==
   #echo 0 >  (...)/01/memory.limit_in_bytes   #set memcg's limit to 0,
   #echo $$ > (...)/01/memory.tasks            #move task
   # do something...
==

(b) seems to be dead lock
==
   #echo 40k >  (...)/01/memory.limit_in_bytes   #set memcg's limit to 0,
   #echo $$ > (...)/01/memory.tasks            #move task
   # do something...
==


I think (a) is BUG. (b) is just slow down.
(you can see pgpgin/pgpgout count is increasing in (B).)

This patch set is for handling (a). Li-san, could you check ?
This works well in my environment.(means OOM-Killer is called in proper way.)

 [1/2].... current mmotm has pagefault_out_of_memory() but this doesn't consider
           memcg. When memcg hit limits in page_fault and panic_on_oom is set,
           the kernel panics.
           This tries to fix that.
           (See patches/mm-invoke-oom-killer-from-page-fault.patch)

 [2/2].... fixes wrong logic of check_under_limit.

Anyway, it seems hierarchy support is *not* enough in OOM handler.
Balbir, could you check it ? 
I think "a bad process in hierarchy rather than memcg" should be killed.

Thanks,
-Kame

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