From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta7.messagelabs.com (mail6.bemta7.messagelabs.com [216.82.255.55]) by kanga.kvack.org (Postfix) with ESMTP id 2ED8D900194 for ; Wed, 22 Jun 2011 20:00:31 -0400 (EDT) Message-ID: <4E028215.90107@redhat.com> Date: Wed, 22 Jun 2011 20:00:21 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH] mmu_notifier, kvm: Introduce dirty bit tracking in spte and mmu notifier to help KSM dirty bit tracking References: <201106212055.25400.nai.xia@gmail.com> <201106212132.39311.nai.xia@gmail.com> <4E01C752.10405@redhat.com> <4E01CC77.10607@ravellosystems.com> <4E01CDAD.3070202@redhat.com> <4E01CFD2.6000404@ravellosystems.com> <4E020CBC.7070604@redhat.com> <20110622165529.GY20843@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Nai Xia Cc: Andrea Arcangeli , Izik Eidus , Avi Kivity , Andrew Morton , Hugh Dickins , Chris Wright , linux-mm , Johannes Weiner , linux-kernel , kvm On 06/22/2011 07:37 PM, Nai Xia wrote: > On 2MB pages, I'd like to remind you and Rik that ksmd currently splits > huge pages before their sub pages gets really merged to stable tree. Your proposal appears to add a condition that causes ksmd to skip doing that, which can cause the system to start using swap instead of sharing memory. > So when there are many 2MB pages each having a 4kB subpage > changed for all time, this is already a concern for ksmd to judge > if it's worthwhile to split 2MB page and get its sub-pages merged. > I think the policy for ksmd in a system should be "If you cannot do sth good, > at least do nothing evil". So I really don't think we can satisfy _all_ people. > Get a general method and give users one or two knobs to tune it when they > are the corner cases. How do you think of my proposal ? I think your proposal makes sense for 4kB pages, but the ksmd policy for 2MB pages probably needs to be much more aggressive. -- All rights reversed -- 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