From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Tippett Subject: Re: sync guest calls made async on host - SQLite performance Date: Sun, 27 Sep 2009 08:07:50 -0400 Message-ID: <4ABF5596.9050207@gmail.com> References: <4ABC6AA5.6080909@tauceti.net> <4ABF4E95.5070100@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: RW , kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from qw-out-2122.google.com ([74.125.92.24]:15903 "EHLO qw-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753844AbZI0MHu (ORCPT ); Sun, 27 Sep 2009 08:07:50 -0400 Received: by qw-out-2122.google.com with SMTP id 5so1349586qwd.37 for ; Sun, 27 Sep 2009 05:07:54 -0700 (PDT) In-Reply-To: <4ABF4E95.5070100@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: I have created a launchpad bug against qemu-kvm in Ubuntu. https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/437473 Just re-iterating, my concern isn't so much performance, but integrity of stock KVM configurations with server or other workloads that expect sync fileIO requests to be honored and synchronous to the underlying physical disk. (That and ensuring that sanity reigns where a benchmark doesn't show a guest operating 10 times faster than a host for the same test :). Regards, Matthew -------- Original Message -------- Subject: Re: sync guest calls made async on host - SQLite performance From: Avi Kivity To: RW Cc: kvm@vger.kernel.org Date: 09/27/2009 07:37 AM > On 09/25/2009 10:00 AM, RW wrote: >> I think ext3 with "data=writeback" in a KVM and KVM started >> with "if=virtio,cache=none" is a little bit crazy. I don't know >> if this is the case with current Ubuntu Alpha but it looks >> like so. >> > > It's not crazy, qemu bypasses the cache with cache=none so the ext3 > data= setting is immaterial. >