From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35? Date: Wed, 04 Aug 2010 19:36:04 +0300 Message-ID: <4C5996F4.6010205@redhat.com> References: <20100803190525.GB16570@redhat.com> <4C586AB9.5040302@codemonkey.ws> <4C586CF9.7030206@redhat.com> <4C588804.5060803@redhat.com> <4C590046.2020705@redhat.com> <4C591D48.9080301@redhat.com> <4C592218.3000901@redhat.com> <4C596549.1070109@codemonkey.ws> <20100804130709.GL10499@redhat.com> <4C5967D8.7080707@codemonkey.ws> <20100804133401.GP10499@redhat.com> <4C5970AC.6060105@codemonkey.ws> <4C5995B4.90505@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , Gerd Hoffmann , "Richard W.M. Jones" , qemu-devel@nongnu.org, kvm@vger.kernel.org To: Anthony Liguori Return-path: Received: from mx1.redhat.com ([209.132.183.28]:53459 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751336Ab0HDQgM (ORCPT ); Wed, 4 Aug 2010 12:36:12 -0400 In-Reply-To: <4C5995B4.90505@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 08/04/2010 07:30 PM, Avi Kivity wrote: > On 08/04/2010 04:52 PM, Anthony Liguori wrote: >>>> >>> This is not like DMA event if done in chunks and chunks can be pretty >>> big. The code that dials with copying may temporary unmap some pci >>> devices to have more space there. >> >> >> That's a bit complicated because SeaBIOS is managing the PCI devices >> whereas the kernel code is running as an option rom. I don't know >> the BIOS PCI interfaces well so I don't know how doable this is. >> >> Maybe we're just being too fancy here. >> >> We could rewrite -kernel/-append/-initrd to just generate a floppy >> image in RAM, and just boot from floppy. > > How could this work? the RAM belongs to SeaBIOS immediately after > reset, it would just scribble over it. Or worse, not scribble on it > until some date in the future. > > -kernel data has to find its way to memory after the bios gives > control to some optionrom. An alternative would be to embed knowledge > of -kernel in seabios, but I don't think it's a good one. > Oh, you meant host RAM, not guest RAM. Disregard. This is basically my suggestion to libguestfs: instead of generating an initrd, generate a bootable cdrom, and boot from that. The result is faster and has a smaller memory footprint. Everyone wins. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=34807 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Oggwv-0000iV-FL for qemu-devel@nongnu.org; Wed, 04 Aug 2010 12:36:14 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1Oggwu-0003Ws-26 for qemu-devel@nongnu.org; Wed, 04 Aug 2010 12:36:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48164) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1Oggwt-0003Wb-R5 for qemu-devel@nongnu.org; Wed, 04 Aug 2010 12:36:12 -0400 Message-ID: <4C5996F4.6010205@redhat.com> Date: Wed, 04 Aug 2010 19:36:04 +0300 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35? References: <20100803190525.GB16570@redhat.com> <4C586AB9.5040302@codemonkey.ws> <4C586CF9.7030206@redhat.com> <4C588804.5060803@redhat.com> <4C590046.2020705@redhat.com> <4C591D48.9080301@redhat.com> <4C592218.3000901@redhat.com> <4C596549.1070109@codemonkey.ws> <20100804130709.GL10499@redhat.com> <4C5967D8.7080707@codemonkey.ws> <20100804133401.GP10499@redhat.com> <4C5970AC.6060105@codemonkey.ws> <4C5995B4.90505@redhat.com> In-Reply-To: <4C5995B4.90505@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, Gerd Hoffmann , Gleb Natapov , "Richard W.M. Jones" On 08/04/2010 07:30 PM, Avi Kivity wrote: > On 08/04/2010 04:52 PM, Anthony Liguori wrote: >>>> >>> This is not like DMA event if done in chunks and chunks can be pretty >>> big. The code that dials with copying may temporary unmap some pci >>> devices to have more space there. >> >> >> That's a bit complicated because SeaBIOS is managing the PCI devices >> whereas the kernel code is running as an option rom. I don't know >> the BIOS PCI interfaces well so I don't know how doable this is. >> >> Maybe we're just being too fancy here. >> >> We could rewrite -kernel/-append/-initrd to just generate a floppy >> image in RAM, and just boot from floppy. > > How could this work? the RAM belongs to SeaBIOS immediately after > reset, it would just scribble over it. Or worse, not scribble on it > until some date in the future. > > -kernel data has to find its way to memory after the bios gives > control to some optionrom. An alternative would be to embed knowledge > of -kernel in seabios, but I don't think it's a good one. > Oh, you meant host RAM, not guest RAM. Disregard. This is basically my suggestion to libguestfs: instead of generating an initrd, generate a bootable cdrom, and boot from that. The result is faster and has a smaller memory footprint. Everyone wins. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.