[Qemu-devel] Re: Slow PXE boot in qemu.git (fast in qemu-kvm.git)

[Luiz Capitulino <lcapitulino@redhat.com>]

On Sat, 9 Apr 2011 13:34:43 +0300
Blue Swirl <blauwirbel@gmail.com> wrote:

> On Sat, Apr 9, 2011 at 2:25 AM, Luiz Capitulino <lcapitulino@redhat.com> 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 :)
> >
> > Ideas?
> 
> What is the test case?

It's an external PXE server, command-line is:

 qemu -boot n -enable-kvm -net nic,model=virtio -net tap,ifname=vnet0,script=

> I tried PXE booting a 10M file with and without
> KVM and the results are pretty much the same with pcnet and e1000.
> time qemu -monitor stdio -boot n -net nic,model=e1000 -net
> user,tftp=.,bootfile=10M -net dump,file=foo -enable-kvm
> time qemu -monitor stdio -boot n -net nic,model=pcnet -net
> user,tftp=.,bootfile=10M -net dump,file=foo -enable-kvm
> time qemu -monitor stdio -boot n -net nic,model=e1000 -net
> user,tftp=.,bootfile=10M -net dump,file=foo
> time qemu -monitor stdio -boot n -net nic,model=pcnet -net
> user,tftp=.,bootfile=10M -net dump,file=foo
> 
> All times are ~10s.

Yeah, you're using the internal tftp server.