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 ESMTP id 96FD06B0074 for ; Mon, 15 Dec 2008 23:27:21 -0500 (EST) Date: Tue, 16 Dec 2008 13:02:30 +0900 From: Daisuke Nishimura Subject: [PATCH mmotm] memcg: fix for documentation (Re: [BUGFIX][PATCH mmotm] memcg fix swap accounting leak (v3)) Message-Id: <20081216130230.2978b8fc.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20081215160751.b6a944be.kamezawa.hiroyu@jp.fujitsu.com> References: <20081212172930.282caa38.kamezawa.hiroyu@jp.fujitsu.com> <20081212184341.b62903a7.nishimura@mxp.nes.nec.co.jp> <46730.10.75.179.61.1229080565.squirrel@webmail-b.css.fujitsu.com> <20081213160310.e9501cd9.kamezawa.hiroyu@jp.fujitsu.com> <4409.10.75.179.62.1229164064.squirrel@webmail-b.css.fujitsu.com> <20081215160751.b6a944be.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: Hugh Dickins , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "balbir@linux.vnet.ibm.com" , "akpm@linux-foundation.org" , nishimura@mxp.nes.nec.co.jp List-ID: Sorry for late reply. > @@ -111,9 +111,40 @@ Under below explanation, we assume CONFI > (b) If the SwapCache has been mapped by processes, it has been > charged already. > > - In case (a), we charge it. In case (b), we don't charge it. > - (But racy state between (a) and (b) exists. We do check it.) > - At charging, a charge recorded in swap_cgroup is moved to page_cgroup. > + This swap-in is one of the most complicated work. In do_swap_page(), > + following events occur when pte is unchanged. > + > + (1) the page (SwapCache) is looked up. > + (2) lock_page() > + (3) try_charge_swapin() > + (4) reuse_swap_page() (may call delete_swap_cache()) > + (5) commit_charge_swapin() > + (6) swap_free(). > + > + Considering following situation for example. > + > + (A) The page has not been charged before (2) and reuse_swap_page() > + doesn't call delete_from_swap_cache(). > + (B) The page has not been charged before (2) and reuse_swap_page() > + calls delete_from_swap_cache(). > + (C) The page has been charged before (2) and reuse_swap_page() doesn't > + call delete_from_swap_cache(). > + (D) The page has been charged before (2) and reuse_swap_page() calls > + delete_from_swap_cache(). > + > + memory.usage/memsw.usage changes to this page/swp_entry will be > + Case (A) (B) (C) (D) > + Event > + Before (2) 0/ 1 0/ 1 1/ 1 1/ 1 > + =========================================== > + (3) +1/+1 +1/+1 +1/+1 +1/+1 > + (4) - 0/ 0 - -1/ 0 > + (5) 0/ 1 0/-1 -1/-1 0/ 0 > + (6) - - - 0/-1 > + =========================================== > + Result 1/ 1 1/1 1/ 1 1/ 1 > + > + In any cases, charges to this page should be 1/ 1. > I've verified that charges will result in valid values by tracing source code in all of these cases, but in case of (B) I don't think commit_charge_swapin does memsw-- because PageSwapCache has been cleared already. swap_free does memsw-- in this case. I attached a fix patch. Thanks, Daisuke Nishimura. === From: Daisuke Nishimura fix for documentation. Signed-off-by: Daisuke Nishimura --- Documentation/controllers/memcg_test.txt | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/Documentation/controllers/memcg_test.txt b/Documentation/controllers/memcg_test.txt index 3c1458a..08d4d3e 100644 --- a/Documentation/controllers/memcg_test.txt +++ b/Documentation/controllers/memcg_test.txt @@ -139,10 +139,10 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y. =========================================== (3) +1/+1 +1/+1 +1/+1 +1/+1 (4) - 0/ 0 - -1/ 0 - (5) 0/ 1 0/-1 -1/-1 0/ 0 - (6) - - - 0/-1 + (5) 0/-1 0/ 0 -1/-1 0/ 0 + (6) - 0/-1 - 0/-1 =========================================== - Result 1/ 1 1/1 1/ 1 1/ 1 + Result 1/ 1 1/ 1 1/ 1 1/ 1 In any cases, charges to this page should be 1/ 1. -- 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