From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uri Lublin Subject: Re: [PATCH] qemu: qemu_fopen_fd: differentiate between reader and writer user Date: Thu, 16 Oct 2008 16:23:40 +0200 Message-ID: <48F74E6C.8070100@il.qumranet.com> References: <1223829030-14962-1-git-send-email-uril@qumranet.com> <48F22BF1.3000608@redhat.com> <48F23D4D.2050709@codemonkey.ws> <48F23F42.10405@redhat.com> <48F277A0.8040407@codemonkey.ws> <48F2BA83.7000101@codemonkey.ws> <48F69AAB.4010404@il.qumranet.com> <48F6BFA1.9070608@codemonkey.ws> <48F6F7AA.2080102@redhat.com> <48F7399B.7000808@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Avi Kivity , Uri Lublin , kvm@vger.kernel.org To: Anthony Liguori Return-path: Received: from il.qumranet.com ([212.179.150.194]:42437 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751856AbYJPOXm (ORCPT ); Thu, 16 Oct 2008 10:23:42 -0400 In-Reply-To: <48F7399B.7000808@codemonkey.ws> Sender: kvm-owner@vger.kernel.org List-ID: Anthony Liguori wrote: > Avi Kivity wrote: >> Anthony Liguori wrote: >>> Uri Lublin wrote: >>>> Anthony Liguori wrote: >>> >>> I have already cut your text, but I don't understand the comment >>> about not being "full duplex". Is there a reason why migration needs >>> to be bidirectional? I don't think there's a fundamental reason it >>> needs to be and I think there are some advantages to it being >>> unidirectional. >>> >> >> Weren't there some acks flowing back on the old protocol to let the >> source now things are fine? > > There were, but there aren't now. They don't improve reliability. > Why do you think they don't improve reliability ? The Ack/Go messages catch the scenario where SRC finishes sending all its state, and DST have a problem loading that state. In that case SRC thinks migration was completed successfully (and stay in stopped mode), while DST exists.