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: Fri, 08 Apr 2011 19:50:57 -0500 Message-ID: <4D9FAD71.5020503@codemonkey.ws> References: <20110408202525.26c45c05@doriath> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, avi@redhat.com, mtosatti@redhat.com, alex.williamson@redhat.com, mst@redhat.com, blauwirbel@gmail.com To: Luiz Capitulino Return-path: Received: from mail-yx0-f174.google.com ([209.85.213.174]:64092 "EHLO mail-yx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757437Ab1DIAvA (ORCPT ); Fri, 8 Apr 2011 20:51:00 -0400 Received: by yxs7 with SMTP id 7so1632615yxs.19 for ; Fri, 08 Apr 2011 17:50:59 -0700 (PDT) In-Reply-To: <20110408202525.26c45c05@doriath> Sender: kvm-owner@vger.kernel.org List-ID: 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 tried with qemu.git v0.13.0 in order to check if this was a regression, but > I got the same problem... > > Then I inspected qemu-kvm.git under the assumption that it could have a fix > that wasn't commited to qemu.git. Found this: > > - commit 0836b77f0f65d56d08bdeffbac25cd6d78267dc9 which is merge, works > > - commit cc015e9a5dde2f03f123357fa060acbdfcd570a4 does not work (it's slow) > > I tried a bisect, but it brakes due to gcc4 vs. gcc3 changes. Then I inspected > commits manually, and found out that commit 64d7e9a4 doesn't work, which makes > me think that the fix could be in the conflict resolution of 0836b77f, which > makes me remember that I'm late for diner, so my conclusions at this point are > not reliable :) Can you run kvm_stat to see what the exit rates are? Maybe we're missing a coalesced io in qemu.git? It's also possible that gpxe is hitting the apic or pit quite a lot. Regards, Anthony Liguori > Ideas? > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html