From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx146.postini.com [74.125.245.146]) by kanga.kvack.org (Postfix) with SMTP id 4F2C06B004A for ; Wed, 18 Apr 2012 03:25:06 -0400 (EDT) Received: from m3.gw.fujitsu.co.jp (unknown [10.0.50.73]) by fgwmail6.fujitsu.co.jp (Postfix) with ESMTP id DBDE93EE0BB for ; Wed, 18 Apr 2012 16:25:04 +0900 (JST) Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id BF76945DEB6 for ; Wed, 18 Apr 2012 16:25:04 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (s3.gw.fujitsu.co.jp [10.0.50.93]) by m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 9859F45DE9E for ; Wed, 18 Apr 2012 16:25:04 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id 7EC591DB8047 for ; Wed, 18 Apr 2012 16:25:04 +0900 (JST) Received: from m106.s.css.fujitsu.com (m106.s.css.fujitsu.com [10.240.81.146]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id C7F921DB8038 for ; Wed, 18 Apr 2012 16:25:03 +0900 (JST) Message-ID: <4F8E6BDC.6050703@jp.fujitsu.com> Date: Wed, 18 Apr 2012 16:23:08 +0900 From: KAMEZAWA Hiroyuki MIME-Version: 1.0 Subject: Re: [RFC][PATCH 2/6] memcg: add pc_set_mem_cgroup_and_flags() References: <4F72EB84.7080000@jp.fujitsu.com> <4F72ED25.60307@jp.fujitsu.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ying Han Cc: "linux-mm@kvack.org" , Linux Kernel , Michal Hocko , Johannes Weiner , Andrew Morton , Glauber Costa , Konstantin Khlebnikov , Suleiman Souhlal (2012/04/18 6:17), Ying Han wrote: > On Wed, Mar 28, 2012 at 3:51 AM, KAMEZAWA Hiroyuki > wrote: >> Consolidate a code for setting pc->mem_cgroup and USED bit which requires smp_wmb(). >> And remove a macro PCGF_NOCOPY_AT_SPLIT which isn't helpful to read code, now. >> >> Signed-off-by: KAMEZAWA Hiroyuki >> --- >> include/linux/page_cgroup.h | 18 ++++++++++++++++++ >> mm/memcontrol.c | 18 ++++-------------- >> 2 files changed, 22 insertions(+), 14 deletions(-) >> >> diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h >> index 92768cb..2707809 100644 >> --- a/include/linux/page_cgroup.h >> +++ b/include/linux/page_cgroup.h >> @@ -1,6 +1,8 @@ >> #ifndef __LINUX_PAGE_CGROUP_H >> #define __LINUX_PAGE_CGROUP_H >> >> +#include >> + >> enum { >> /* flags for mem_cgroup */ >> PCG_LOCK, /* Lock for pc->mem_cgroup and following bits. */ >> @@ -94,6 +96,22 @@ pc_set_mem_cgroup(struct page_cgroup *pc, struct mem_cgroup *memcg) >> pc->mem_cgroup = memcg; >> } >> >> +static inline void >> +pc_set_mem_cgroup_and_flags(struct page_cgroup *pc, struct mem_cgroup *memcg, >> + unsigned long flags) >> +{ >> + pc->mem_cgroup = memcg; >> + /* >> + * We access a page_cgroup asynchronously without lock_page_cgroup(). >> + * Especially when a page_cgroup is taken from a page, pc's mem_cgroup >> + * is accessed after testing USED bit. To make pc's mem_cgroup visible >> + * before USED bit, we need memory barrier here. >> + * See mem_cgroup_add_lru_list(), etc. >> + */ >> + smp_wmb(); >> + pc->flags = flags; >> +} >> + >> #else /* CONFIG_CGROUP_MEM_RES_CTLR */ >> struct page_cgroup; >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 8077460..d366b60 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -2511,16 +2511,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg, >> } >> } >> >> - pc_set_mem_cgroup(pc, memcg); >> - /* >> - * We access a page_cgroup asynchronously without lock_page_cgroup(). >> - * Especially when a page_cgroup is taken from a page, pc's mem_cgroup >> - * is accessed after testing USED bit. To make pc's mem_cgroup visible >> - * before USED bit, we need memory barrier here. >> - * See mem_cgroup_add_lru_list(), etc. >> - */ >> - smp_wmb(); >> - SetPageCgroupUsed(pc); > > I might be confused. We removed this SetPageCgroupUsed() but not > adding it back elsewhere ? > > --Ying > >> + pc_set_mem_cgroup_and_flags(pc, memcg, BIT(PCG_USED) | BIT(PCG_LOCK)); Added here. This sets | memcg pointer | Used | Locked | 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org