From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx129.postini.com [74.125.245.129]) by kanga.kvack.org (Postfix) with SMTP id 48D296B0085 for ; Mon, 16 Jan 2012 07:55:07 -0500 (EST) Date: Mon, 16 Jan 2012 14:55:26 +0200 From: "Kirill A. Shutemov" Subject: Re: [RFC] [PATCH 3/7 v2] memcg: remove PCG_MOVE_LOCK flag from pc->flags Message-ID: <20120116125526.GB25981@shutemov.name> References: <20120113173001.ee5260ca.kamezawa.hiroyu@jp.fujitsu.com> <20120113174019.8dff3fc1.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120113174019.8dff3fc1.kamezawa.hiroyu@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org List-ID: To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , Ying Han , "hugh.dickins@tiscali.co.uk" , "hannes@cmpxchg.org" , Michal Hocko , cgroups@vger.kernel.org, "bsingharora@gmail.com" On Fri, Jan 13, 2012 at 05:40:19PM +0900, KAMEZAWA Hiroyuki wrote: > > From 1008e84d94245b1e7c4d237802ff68ff00757736 Mon Sep 17 00:00:00 2001 > From: KAMEZAWA Hiroyuki > Date: Thu, 12 Jan 2012 15:53:24 +0900 > Subject: [PATCH 3/7] memcg: remove PCG_MOVE_LOCK flag from pc->flags. > > PCG_MOVE_LOCK bit is used for bit spinlock for avoiding race between > memcg's account moving and page state statistics updates. > > Considering page-statistics update, very hot path, this lock is > taken only when someone is moving account (or PageTransHuge()) > And, now, all moving-account between memcgroups (by task-move) > are serialized. > > So, it seems too costly to have 1bit per page for this purpose. > > This patch removes PCG_MOVE_LOCK and add hashed rwlock array > instead of it. This works well enough. Even when we need to > take the lock, we don't need to disable IRQ in hot path because > of using rwlock. > > Signed-off-by: KAMEZAWA Hiroyuki ... > +#define NR_MOVE_ACCOUNT_LOCKS (NR_CPUS) > +#define move_account_hash(page) ((page_to_pfn(page) % NR_MOVE_ACCOUNT_LOCKS)) You still tend to add too many parentheses into macros ;) -- Kirill A. Shutemov -- 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