From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Tippett Subject: sync guest calls made async on host - SQLite performance Date: Wed, 23 Sep 2009 11:58:54 -0400 Message-ID: <4ABA45BE.1080008@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: kvm@vger.kernel.org Return-path: Received: from fg-out-1718.google.com ([72.14.220.159]:31244 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751059AbZIWP6z (ORCPT ); Wed, 23 Sep 2009 11:58:55 -0400 Received: by fg-out-1718.google.com with SMTP id 22so288546fge.1 for ; Wed, 23 Sep 2009 08:58:58 -0700 (PDT) Sender: kvm-owner@vger.kernel.org List-ID: Hi, I would like to call attention to the SQLite performance under KVM in the current Ubuntu Alpha. http://www.phoronix.com/scan.php?page=article&item=linux_2631_kvm&num=3 SQLite's benchmark as part of the Phoronix Test Suite is typically IO limited and is affected by both disk and filesystem performance. When comparing SQLite under the host against the guest OS, there is an order of magnitude _IMPROVEMENT_ in the measured performance of the guest. I am expecting that the host is doing synchronous IO operations but somewhere in the stack the calls are ultimately being made asynchronous or at the very least batched for writing. On the surface, this represents a data integrity issue and I am interested in the KVM communities thoughts on this behaviour. Is it expected? Is it acceptable? Is it safe? Regards, Matthew