From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=45284 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OghuQ-0005d8-5z for qemu-devel@nongnu.org; Wed, 04 Aug 2010 13:37:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OghuO-0004iI-Om for qemu-devel@nongnu.org; Wed, 04 Aug 2010 13:37:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57087) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OghuO-0004i6-HG for qemu-devel@nongnu.org; Wed, 04 Aug 2010 13:37:40 -0400 Date: Wed, 4 Aug 2010 20:37:37 +0300 From: Gleb Natapov Subject: Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35? Message-ID: <20100804173737.GC19348@redhat.com> References: <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> <4C5996F4.6010205@redhat.com> <4C5998F1.4030001@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4C5998F1.4030001@codemonkey.ws> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: qemu-devel@nongnu.org, "Richard W.M. Jones" , Avi Kivity , kvm@vger.kernel.org, Gerd Hoffmann On Wed, Aug 04, 2010 at 11:44:33AM -0500, Anthony Liguori wrote: > On 08/04/2010 11:36 AM, Avi Kivity wrote: > > 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. > > Yeah, but we could also do that entirely in QEMU. If that's what we > suggest doing, there's no reason not to do it instead of the option > rom trickery that we do today. > > The option rom stuff has a number of short comings. Because we > hijack int19, extboot doesn't get to run. That means that if you > use -kernel to load a grub (the Ubuntu guys for their own absurd > reasons) then grub does not see extboot backed disks. The solution > for them is the same, generate a proper disk and boot from that > disk. > Extboot is not so relevant any more. -- Gleb.