From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: Slow PXE boot in qemu.git (fast in qemu-kvm.git) Date: Mon, 11 Apr 2011 19:39:44 -0500 Message-ID: <4DA39F50.8090108@codemonkey.ws> 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=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Luiz Capitulino , Alex Williamson , 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 mail-gy0-f174.google.com ([209.85.160.174]:64756 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756467Ab1DLAjr (ORCPT ); Mon, 11 Apr 2011 20:39:47 -0400 Received: by gyd10 with SMTP id 10so2363991gyd.19 for ; Mon, 11 Apr 2011 17:39:46 -0700 (PDT) In-Reply-To: <4DA35EE4.6090303@web.de> Sender: kvm-owner@vger.kernel.org List-ID: On 04/11/2011 03:04 PM, 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. If gpxe is spinning waiting for I/O to complete, that's going to prevent select from running until the next signal (timer event). Regards, Anthony Liguori > Jan >