From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx148.postini.com [74.125.245.148]) by kanga.kvack.org (Postfix) with SMTP id 0DA536B004F for ; Wed, 18 Jan 2012 18:54:26 -0500 (EST) Received: from m3.gw.fujitsu.co.jp (unknown [10.0.50.73]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id 2E59B3EE0BD for ; Thu, 19 Jan 2012 08:54:25 +0900 (JST) Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 13ABB45DEB5 for ; Thu, 19 Jan 2012 08:54:25 +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 EAFA745DE9E for ; Thu, 19 Jan 2012 08:54:24 +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 DA25B1DB803F for ; Thu, 19 Jan 2012 08:54:24 +0900 (JST) Received: from m107.s.css.fujitsu.com (m107.s.css.fujitsu.com [10.240.81.147]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id 91E921DB803B for ; Thu, 19 Jan 2012 08:54:24 +0900 (JST) Date: Thu, 19 Jan 2012 08:53:09 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [RFC] [PATCH 3/7 v2] memcg: remove PCG_MOVE_LOCK flag from pc->flags Message-Id: <20120119085309.616cadb4.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20120118104703.GA31112@tiehlicka.suse.cz> References: <20120113173001.ee5260ca.kamezawa.hiroyu@jp.fujitsu.com> <20120113174019.8dff3fc1.kamezawa.hiroyu@jp.fujitsu.com> <20120117164605.GB22142@tiehlicka.suse.cz> <20120118091226.b46e0f6e.kamezawa.hiroyu@jp.fujitsu.com> <20120118104703.GA31112@tiehlicka.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: "linux-mm@kvack.org" , Ying Han , "hugh.dickins@tiscali.co.uk" , "hannes@cmpxchg.org" , cgroups@vger.kernel.org, "bsingharora@gmail.com" On Wed, 18 Jan 2012 11:47:03 +0100 Michal Hocko wrote: > On Wed 18-01-12 09:12:26, KAMEZAWA Hiroyuki wrote: > > On Tue, 17 Jan 2012 17:46:05 +0100 > > Michal Hocko wrote: > > > > > On Fri 13-01-12 17:40:19, KAMEZAWA Hiroyuki wrote: > [...] > > > > 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, > > > > > > Hmmm, rwlocks are not popular these days very much. > > > Anyway, can we rather make it (source) memcg (bit)spinlock instead. We > > > would reduce false sharing this way and would penalize only pages from > > > the moving group. > > > > > per-memcg spinlock ? > > Yes > > > The reason I used rwlock() is to avoid disabling IRQ. This routine > > will be called by IRQ context (for dirty ratio support). So, IRQ > > disable will be required if we use spinlock. > > OK, I have missed the comment about disabling IRQs. It's true that we do > not have to be afraid about deadlocks if the lock is held only for > reading from the irq context but does the spinlock makes a performance > bottleneck? We are talking about the slowpath. > I could see the reason for the read lock when doing hashed locks because > they are global but if we make the lock per memcg then we shouldn't > interfere with other updates which are not blocked by the move. > Hm, ok. In the next version, I'll use per-memcg spinlock (with hash if necessary) 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