From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 5CEF66B00D3 for ; Mon, 27 Apr 2009 19:58:33 -0400 (EDT) Received: from m6.gw.fujitsu.co.jp ([10.0.50.76]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n3RNxQdp013182 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Tue, 28 Apr 2009 08:59:26 +0900 Received: from smail (m6 [127.0.0.1]) by outgoing.m6.gw.fujitsu.co.jp (Postfix) with ESMTP id 0CBED45DE4F for ; Tue, 28 Apr 2009 08:59:26 +0900 (JST) Received: from s6.gw.fujitsu.co.jp (s6.gw.fujitsu.co.jp [10.0.50.96]) by m6.gw.fujitsu.co.jp (Postfix) with ESMTP id D9E2B45DD72 for ; Tue, 28 Apr 2009 08:59:25 +0900 (JST) Received: from s6.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s6.gw.fujitsu.co.jp (Postfix) with ESMTP id C7597E18004 for ; Tue, 28 Apr 2009 08:59:25 +0900 (JST) Received: from m105.s.css.fujitsu.com (m105.s.css.fujitsu.com [10.249.87.105]) by s6.gw.fujitsu.co.jp (Postfix) with ESMTP id 7D9A6E18002 for ; Tue, 28 Apr 2009 08:59:25 +0900 (JST) Date: Tue, 28 Apr 2009 08:57:53 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH] fix leak of swap accounting as stale swap cache under memcg Message-Id: <20090428085753.a91b6007.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <661de9470904271217t7ef9e300x1e40bbf0362ca14f@mail.gmail.com> References: <20090427181259.6efec90b.kamezawa.hiroyu@jp.fujitsu.com> <20090427101323.GK4454@balbir.in.ibm.com> <20090427203535.4e3f970b.d-nishimura@mtf.biglobe.ne.jp> <661de9470904271217t7ef9e300x1e40bbf0362ca14f@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Balbir Singh Cc: nishimura@mxp.nes.nec.co.jp, "linux-mm@kvack.org" , "hugh@veritas.com" , "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" List-ID: On Tue, 28 Apr 2009 00:47:31 +0530 Balbir Singh wrote: > Thanks for the detailed explanation of the possible race conditions. I > am beginning to wonder why we don't have any hooks in add_to_swap.*. > for charging a page. If the page is already charged and if it is a > context issue (charging it to the right cgroup) that is already > handled from what I see. Won't that help us solve the !PageCgroupUsed > issue? > For adding hook to add_to_swap_cache, we need to know which cgroup the swap cache should be charged. Then, we have to remove CONFIG_CGROUP_MEM_RES_CTRL_SWAP_EXT and enable memsw control always. When using swap_cgroup, we'll know which cgroup the new swap cache should be charged. Then, the new page readed in will be charged to recorded cgroup in swap_cgroup. One bad thing of this method is a cgroup which swap_cgroup point to is different from a cgroup which the task calls do_swap_fault(). This means that a page-fault by a task can cause memory-reclaim under another cgroup and moreover, OOM. I don't think it's sane behavior. So, current design of swap accounting waits until the page is mapped. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org