From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 6B8916B003D for ; Mon, 9 Mar 2009 23:36:47 -0400 (EDT) Date: Tue, 10 Mar 2009 12:18:56 +0900 From: Daisuke Nishimura Subject: Re: [BUGFIX][PATCH] memcg: charge swapcache to proper memcg Message-Id: <20090310121856.93cd2786.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20090310113502.d272fc2a.kamezawa.hiroyu@jp.fujitsu.com> References: <20090310100707.e0640b0b.nishimura@mxp.nes.nec.co.jp> <20090310113502.d272fc2a.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: nishimura@mxp.nes.nec.co.jp, Andrew Morton , linux-mm , Balbir Singh , Li Zefan , Hugh Dickins List-ID: On Tue, 10 Mar 2009 11:35:02 +0900, KAMEZAWA Hiroyuki wrote: > On Tue, 10 Mar 2009 10:07:07 +0900 > Daisuke Nishimura wrote: > > > From: Daisuke Nishimura > > > > memcg_test.txt says at 4.1: > > > > 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/ 0 -1/-1 0/ 0 > > (6) - 0/-1 - 0/-1 > > =========================================== > > Result 1/ 1 1/ 1 1/ 1 1/ 1 > > > > In any cases, charges to this page should be 1/ 1. > > > > In case of (D), mem_cgroup_try_get_from_swapcache() returns NULL > > (because lookup_swap_cgroup() returns NULL), so "+1/+1" at (3) means > > charges to the memcg("foo") to which the "current" belongs. > > Hmm...in try_charge_swapin(), if !PageSwapCache(), > it seems no charges and returns NULL...(means commit will not occur.) > Could you clarify ? > I'm saying about PageSwapCache() case. IIUC, swapcache which has been unmapped but has not been removed from swapcache yet on swap-out path (so not uncharged yet) can go through this (D) path. Thanks, Daisuke Nishimura. -- 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