From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: Re: Slow PXE boot in qemu.git (fast in qemu-kvm.git) Date: Mon, 11 Apr 2011 14:14:08 -0600 Message-ID: <1302552848.3589.89.camel@x201> References: <20110408202525.26c45c05@doriath> <4D9FAD71.5020503@codemonkey.ws> <20110411153519.37f8316a@doriath> <1302548432.3589.78.camel@x201> <20110411161555.49688970@doriath> <4DA35EE4.6090303@web.de> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Luiz Capitulino , Anthony Liguori , qemu-devel@nongnu.org, kvm@vger.kernel.org, avi@redhat.com, mtosatti@redhat.com, mst@redhat.com, blauwirbel@gmail.com To: Jan Kiszka Return-path: Received: from mx1.redhat.com ([209.132.183.28]:32752 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755846Ab1DKUON (ORCPT ); Mon, 11 Apr 2011 16:14:13 -0400 In-Reply-To: <4DA35EE4.6090303@web.de> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, 2011-04-11 at 22:04 +0200, Jan Kiszka wrote: > On 2011-04-11 21:15, Luiz Capitulino wrote: > > On Mon, 11 Apr 2011 13:00:32 -0600 > > Alex Williamson wrote: > > > >> On Mon, 2011-04-11 at 15:35 -0300, Luiz Capitulino wrote: > >>> On Fri, 08 Apr 2011 19:50:57 -0500 > >>> Anthony Liguori wrote: > >>> > >>>> On 04/08/2011 06:25 PM, Luiz Capitulino wrote: > >>>>> Hi there, > >>>>> > >>>>> Summary: > >>>>> > >>>>> - PXE boot in qemu.git (HEAD f124a41) is quite slow, more than 5 minutes. Got > >>>>> the problem with e1000, virtio and rtl8139. However, pcnet *works* (it's > >>>>> as fast as qemu-kvm.git) > >>>>> > >>>>> - PXE boot in qemu-kvm.git (HEAD df85c051) is fast, less than a minute. Tried > >>>>> with e1000, virtio and rtl8139 (I don't remember if I tried with pcnet) > >>>>> > >> > >> I was having this problem too, but I think it's because I forgot to > >> build qemu with --enable-io-thread, which is the default for qemu-kvm. > >> Can you re-configure and build with that and see if it's fast? Thanks, > > > > Yes, nice catch, it's faster with I/O thread enabled, even seem faster > > than qemu-kvm.git. > > What's the performance under qemu-kvm with -no-kvm-irqchip? > > > > > So, does this have to be fixed w/o I/O thread? > > If it's most probably an architectural deficit of non-io-thread mode, I > would say let it rest in peace. But maybe it points to a generic issues > that is just magnified by non-threaded mode. I've probably been told, but forget. Why isn't io-thread enabled by default? Thanks, Alex