From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 59DE86007BF for ; Wed, 2 Dec 2009 00:09:04 -0500 (EST) Message-ID: <4B15F642.1080308@redhat.com> Date: Wed, 02 Dec 2009 00:08:18 -0500 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 2/9] ksm: let shared pages be swappable References: <20091201181633.5C31.A69D9226@jp.fujitsu.com> <20091201093738.GL30235@random.random> <20091201184535.5C37.A69D9226@jp.fujitsu.com> <20091201095947.GM30235@random.random> In-Reply-To: <20091201095947.GM30235@random.random> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Andrea Arcangeli Cc: KOSAKI Motohiro , KAMEZAWA Hiroyuki , Hugh Dickins , Andrew Morton , Izik Eidus , Chris Wright , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On 12/01/2009 04:59 AM, Andrea Arcangeli wrote: > On Tue, Dec 01, 2009 at 06:46:06PM +0900, KOSAKI Motohiro wrote: > >> Ah, well. please wait a bit. I'm under reviewing Larry's patch. I don't >> dislike your idea. last mail only pointed out implementation thing. >> > Yep thanks for pointing it out. It's an implementation thing I don't > like. The VM should not ever touch ptes when there's light VM pressure > and plenty of unmapped clean cache available, but I'm ok if others > disagree and want to keep it that way. > The VM needs to touch a few (but only a few) PTEs in that situation, to make sure that anonymous pages get moved to the inactive anon list and get to a real chance at being referenced before we try to evict anonymous pages. Without a small amount of pre-aging, we would end up essentially doing FIFO replacement of anonymous memory, which has been known to be disastrous to performance for over 40 years now. A two-handed clock mechanism needs to put some distance between the front and the back hands of the clock. Having said that - it may be beneficial to keep very heavily shared pages on the active list, without ever trying to scan the ptes associated with them. -- 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