From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:58264) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TYSat-0000Lg-9D for qemu-devel@nongnu.org; Tue, 13 Nov 2012 21:20:50 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TYSaq-0005U7-5y for qemu-devel@nongnu.org; Tue, 13 Nov 2012 21:20:47 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50937) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TYSap-0005U1-Pa for qemu-devel@nongnu.org; Tue, 13 Nov 2012 21:20:44 -0500 Message-ID: <50A2FFD8.1050909@redhat.com> Date: Wed, 14 Nov 2012 03:20:08 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <87390dcw7l.fsf@trasno.org> <50A27528.2030900@redhat.com> <50A27EBF.3090402@redhat.com> <50A2806E.20605@redhat.com> <20121114021422.GI12124@valinux.co.jp> In-Reply-To: <20121114021422.GI12124@valinux.co.jp> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] Migration ToDo list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Isaku Yamahata Cc: quintela@redhat.com, qemu-devel qemu-devel , Michael Roth , Orit Wasserman , benoit.hudzia@sap.com, chegu_vinod@hp.com Il 14/11/2012 03:14, Isaku Yamahata ha scritto: >> > Identifying ballooned zero pages is useful, because those cause the >> > clear_page calls in the kernel even in a guest that has been running for >> > a while. >> > >> > But a generic solution doesn't really matter, because is_dup_page and >> > clear_page shouldn't really be in the profile in practice, except in >> > microbenchmarks. > I guess mincore(2) can be used as easy way to detect non-mapped page. > This is just implementation detail anyway. Doesn't work if the page is swapped, doesn't it? But I wonder if the clear_page occurrences are because of the problem described recently on LWN (http://lwn.net/Articles/517465/), and so really more of a kernel bug than anything else. Paolo