From mboxrd@z Thu Jan 1 00:00:00 1970 From: "=?utf-8?B?WmhhbmcgSGFveXU=?=" Subject: =?utf-8?B?UmU6IFNvbWUgbW9yZSBiYXNpYyBxdWVzdGlvbnMuLg==?= Date: Tue, 3 Jun 2014 11:43:19 +0800 Message-ID: <201406031143173652147@sangfor.com> References: , <201405291445129559886@sangfor.com>, , <201405301448239589273@sangfor.com>, Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: "=?utf-8?B?a3Zt?=" To: "=?utf-8?B?TWFyY3VzIFdoaXRl?=" Return-path: Received: from smtp.sanfor.com ([58.251.49.30]:39785 "EHLO mail.sangfor.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752100AbaFCDnf (ORCPT ); Mon, 2 Jun 2014 23:43:35 -0400 Sender: kvm-owner@vger.kernel.org List-ID: >A few additional questions:) > >1. If IO to a block device goes through QEMU and not vhost, are there >data copies between kernel and user mode if I do IO to a block device >or is it zero copy? Kind of related to Question (2) also. > I'm not sure, it perhaps depend on which IO mode you chose, qemu pthreads IO, or linux AIO? Somebody else do a favour, please. >2. A related question to (1), is the QEMU process separate from the VM >process or do they all run on the same process as different threads? I >did read about IO threads and it seemed like they are all part of the >same process, wanted to confirm. > Yes, vcpu threads and qemu backend IO threads belong to the same process(qemu). >Thank you:)