From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35? Date: Tue, 03 Aug 2010 11:46:05 -0500 Message-ID: <4C5847CD.9080107@codemonkey.ws> References: <20100803111306.GA21886@amd.home.annexia.org> <20100803113302.GT24773@redhat.com> <20100803121000.GV13789@amd.home.annexia.org> <20100803123714.GU24773@redhat.com> <20100803124808.GW13789@amd.home.annexia.org> <4C58176B.2050306@redhat.com> <20100803140506.GD22211@amd.home.annexia.org> <4C5829E1.60004@redhat.com> <20100803145337.GF22211@amd.home.annexia.org> <4C583F6A.7030600@redhat.com> <20100803162857.GX13789@amd.home.annexia.org> <4C584781.9040609@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "Richard W.M. Jones" , qemu-devel@nongnu.org, Gleb Natapov , kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from mail-qy0-f174.google.com ([209.85.216.174]:59335 "EHLO mail-qy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755699Ab0HCQqJ (ORCPT ); Tue, 3 Aug 2010 12:46:09 -0400 Received: by qyk7 with SMTP id 7so309342qyk.19 for ; Tue, 03 Aug 2010 09:46:09 -0700 (PDT) In-Reply-To: <4C584781.9040609@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 08/03/2010 11:44 AM, Avi Kivity wrote: > On 08/03/2010 07:28 PM, Richard W.M. Jones wrote: >> On Tue, Aug 03, 2010 at 07:10:18PM +0300, Avi Kivity wrote: >>> -kernel and -initrd is a developer's interface intended to make life >>> easier for users that use qemu to develop kernels. It was not >>> intended as a high performance DMA engine. Neither was the firmware >>> _configuration_ interface. That is what virtio and to a lesser >>> extent IDE was written to perform. You'll get much better results >>> from them. >> Firmware configuration replaced something which was already working >> really fast -- preloading the images into memory -- with something >> which worked slower, and has just recently got _way_ more slow. >> >> This is a regression. Plain and simple. > > It's only a regression if there was any intent at making this a > performant interface. Otherwise any change an be interpreted as a > regression. Even "binary doesn't hash to exact same signature" is a > regression. > >> I have posted a small patch which makes this 650x faster without >> appreciable complication. > > It doesn't appear to support live migration, or hiding the feature for > -M older. > > It's not a good path to follow. Tomorrow we'll need to load 300MB > initrds and we'll have to rework this yet again. Meanwhile the kernel > and virtio support demand loading of any image size you'd want to use. firmware is totally broken with respect to -M older FWIW. Regards, Anthony Liguori