From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id E41D660021B for ; Tue, 8 Dec 2009 19:46:31 -0500 (EST) Received: from m5.gw.fujitsu.co.jp ([10.0.50.75]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id nB90kTCk017842 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Wed, 9 Dec 2009 09:46:29 +0900 Received: from smail (m5 [127.0.0.1]) by outgoing.m5.gw.fujitsu.co.jp (Postfix) with ESMTP id E39DB45DE51 for ; Wed, 9 Dec 2009 09:46:28 +0900 (JST) Received: from s5.gw.fujitsu.co.jp (s5.gw.fujitsu.co.jp [10.0.50.95]) by m5.gw.fujitsu.co.jp (Postfix) with ESMTP id C62C945DE4F for ; Wed, 9 Dec 2009 09:46:28 +0900 (JST) Received: from s5.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s5.gw.fujitsu.co.jp (Postfix) with ESMTP id ACDC4E1800A for ; Wed, 9 Dec 2009 09:46:28 +0900 (JST) Received: from m108.s.css.fujitsu.com (m108.s.css.fujitsu.com [10.249.87.108]) by s5.gw.fujitsu.co.jp (Postfix) with ESMTP id 59F0D1DB803F for ; Wed, 9 Dec 2009 09:46:25 +0900 (JST) Date: Wed, 9 Dec 2009 09:43:31 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH 2/9] ksm: let shared pages be swappable Message-Id: <20091209094331.a1f53e6d.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20091204171640.GE19624@x200.localdomain> References: <20091202125501.GD28697@random.random> <20091203134610.586E.A69D9226@jp.fujitsu.com> <20091204135938.5886.A69D9226@jp.fujitsu.com> <20091204141617.f4c491e7.kamezawa.hiroyu@jp.fujitsu.com> <20091204171640.GE19624@x200.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Chris Wright Cc: KOSAKI Motohiro , Andrea Arcangeli , Rik van Riel , Hugh Dickins , Andrew Morton , Izik Eidus , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Fri, 4 Dec 2009 09:16:40 -0800 Chris Wright wrote: > * KAMEZAWA Hiroyuki (kamezawa.hiroyu@jp.fujitsu.com) wrote: > > KOSAKI Motohiro wrote: > > > Windows kernel have zero page thread and it clear the pages in free list > > > periodically. because many windows subsystem prerefer zero filled page. > > > hen, if we use windows guest, zero filled page have plenty mapcount rather > > > than other typical sharing pages, I guess. > > > > > > So, can we mark as unevictable to zero filled ksm page? > > That's why I mentioned the page of zeroes as the prime example of > something with a high mapcount that shouldn't really ever be evicted. > > > Hmm, can't we use ZERO_PAGE we have now ? > > If do so, > > - no mapcount check > > - never on LRU > > - don't have to maintain shared information because ZERO_PAGE itself has > > copy-on-write nature. > > It's a somewhat special case, but wouldn't it be useful to have a generic > method to recognize this kind of sharing since it's a generic issue? > I just remembered that why ZERO_PAGE was removed (in past). It was becasue cache-line ping-pong at fork beacause of page->mapcount. And KSM introduces zero-pages which have mapcount again. If no problems in realitsitc usage of KVM, ignore me. 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/ . Don't email: email@kvack.org