From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ryan Harper Subject: Re: Poor write- and overall performance Date: Fri, 19 Dec 2008 23:19:00 -0600 Message-ID: <20081220051900.GY13481@us.ibm.com> References: <49459A51.7040905@opengeo.org> <4945FB64.3040109@redhat.com> <494C4DF7.30106@opengeo.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm@vger.kernel.org To: Arne Kepp Return-path: Received: from e3.ny.us.ibm.com ([32.97.182.143]:59412 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750727AbYLTFTD (ORCPT ); Sat, 20 Dec 2008 00:19:03 -0500 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by e3.ny.us.ibm.com (8.13.1/8.13.1) with ESMTP id mBK5I8VK014521 for ; Sat, 20 Dec 2008 00:18:08 -0500 Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id mBK5J1nR198836 for ; Sat, 20 Dec 2008 00:19:01 -0500 Received: from d01av01.pok.ibm.com (loopback [127.0.0.1]) by d01av01.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id mBK5J1A8030028 for ; Sat, 20 Dec 2008 00:19:01 -0500 Content-Disposition: inline In-Reply-To: <494C4DF7.30106@opengeo.org> Sender: kvm-owner@vger.kernel.org List-ID: * Arne Kepp [2008-12-19 19:45]: > Avi Kivity wrote: > >Arne Kepp wrote: > >>Hi, > >> > >>I'm testing KVM 80 (prepackaged from lfarkas.org) on CentOS 5.2 (both > >>guest and host) and comparing against Xen 3.3.0. The only > >>modification I've really made is that I've set noatime on both guest > >>and host. The guest is running straight from an LVM volume and is > >>assigned 4 Gb RAM and 4 virtual CPUs. > > > >I suggest trying scsi in kvm-81, or setting cache=writeback if you > >want to keep using IDE (but be aware of the potential for severe data > >loss with the latter option). > > > > Thanks for the tip. I tested with the SCSI driver and 81, unfortunately > write performance was approximately the same as before. Yeah, currently the scsi emulation doesn't queue up writes, rather it waits for each one to complete which means one cannot take advantage of the aio infrastructure. I'm currently working on fixing this; stay tuned. -- Ryan Harper Software Engineer; Linux Technology Center IBM Corp., Austin, Tx ryanh@us.ibm.com