From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35863) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XtIwX-0003EH-Tu for qemu-devel@nongnu.org; Tue, 25 Nov 2014 11:26:26 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XtIwS-0002qn-Qf for qemu-devel@nongnu.org; Tue, 25 Nov 2014 11:26:21 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33522) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XtIwS-0002qV-Fn for qemu-devel@nongnu.org; Tue, 25 Nov 2014 11:26:16 -0500 Date: Tue, 25 Nov 2014 16:25:58 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20141125162558.GK2550@work-vm> References: <1412358473-31398-1-git-send-email-dgilbert@redhat.com> <1412358473-31398-43-git-send-email-dgilbert@redhat.com> <20141113030105.GD7291@voom.fritz.box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141113030105.GD7291@voom.fritz.box> Subject: Re: [Qemu-devel] [PATCH v4 42/47] Don't sync dirty bitmaps in postcopy List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson Cc: aarcange@redhat.com, yamahata@private.email.ne.jp, quintela@redhat.com, cristian.klein@cs.umu.se, qemu-devel@nongnu.org, amit.shah@redhat.com, yanghy@cn.fujitsu.com * David Gibson (david@gibson.dropbear.id.au) wrote: > On Fri, Oct 03, 2014 at 06:47:48PM +0100, Dr. David Alan Gilbert (git) wrote: > > From: "Dr. David Alan Gilbert" > > > > Once we're in postcopy the source processors are stopped and memory > > shouldn't change any more, so there's no need to look at the dirty > > map. > > > > There are two notes to this: > > 1) If we do resync and a page had changed then the page would get > > sent again, which the destination wouldn't allow (since it might > > have also modified the page) > > 2) Before disabling this I'd seen very rare cases where a page had been > > marked dirtied although the memory contents are apparently identical > > It would be nice to understand how that happened. Yes, I'd come to the conclusion it was a device that was prodding about in user memory space even though it should have stopped, although I hadn't gone and traced them down. Dave > > > Signed-off-by: Dr. David Alan Gilbert > > Otherwise, > > Reviewed-by: David Gibson > > -- > David Gibson | I'll have my music baroque, and my code > david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ > | _way_ _around_! > http://www.ozlabs.org/~dgibson -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK